WO2019139337A1 - Motherboard, method for fabrication of compound semiconductor solar cell by using same motherboard, and compound semiconductor solar cell - Google Patents

Abstract

The present invention relates to a motherboard, a method for fabrication of a compound semiconductor solar cell by using the motherboard, and a compound semiconductor solar cell. A motherboard according to an aspect of the present invention comprises a GaAs single crystal wafer or a Ge single crystal wafer; and a metamorphic layer being physically in direct contact with one surface of the GaAs single crystal wafer or the Ge single crystal wafer and changing in lattice constant with thickness directions. Of the opposite surfaces of the metamorphic layer, a first surface in contact with the GaAs single crystal wafer or the Ge single crystal wafer is formed to have a smaller lattice constant than that of a second surface opposite to the first surface and the lattice constant of the metamorphic layer may increase in a stepwise, exponential, or logarithmic manner from the first surface to the second surface.

Description

A mother substrate, a method for manufacturing a compound semiconductor solar cell using the mother substrate, and a compound semiconductor solar cell

The present invention relates to a mosquito board, a method of manufacturing a compound semiconductor solar cell using the mother board, and a compound semiconductor solar cell, and more particularly, to a mosquito board capable of producing a high efficiency compound semiconductor solar cell, A method of manufacturing a compound semiconductor solar cell, and a compound semiconductor solar cell.

The compound semiconductor is not a single element such as silicon or germanium, but two or more elements are combined to operate as a semiconductor. Currently, various kinds of compound semiconductors have been developed and used in various fields. Typical examples of such compound semiconductors include light emitting devices such as light emitting diodes and laser diodes using solar cells, solar cells, and thermoelectric conversion devices using Peltier effect .

Among them, the compound semiconductor solar cell is composed of gallium arsenide (hereinafter referred to as GaAs), gallium indium phosphor (hereinafter referred to as GaInP), gallium aluminum arsenide (hereinafter referred to as GaAlAs), gallium indium arsenide II-VI compound semiconductors such as cadmium sulphide (CdS), cadmium tellurium (CdTe), zinc sulfide (ZnS), and the like; I-III-VI compound semiconductors typified by copper indium-selenium (CuInSe2) or the like are used to form various layers.

(Hereinafter referred to as a compound semiconductor layer) may be formed by a metal organic chemical vapor deposition (MOCVD) method, an MBE (Molecular Beam Epitaxy) method, or any other suitable method for forming an epitaxial layer. The compound semiconductor layer formed on the mother substrate and formed on the mother substrate is formed as a single junction structure or a multiple junction structure.

Here, the single-junction compound semiconductor layer is for forming a compound semiconductor solar cell having a single junction structure, and the compound semiconductor solar cell having a single junction structure has one cell including a base layer and an emitter layer do.

The compound semiconductor layer of the multiple junction structure is for forming a compound semiconductor solar cell having a multi junction structure, and the compound semiconductor solar cell of the multiple junction structure comprises two or more cells including the base layer and the emitter layer.

Therefore, a compound semiconductor solar cell having a double junction structure has a bottom cell and a top cell, and a compound semiconductor solar cell having a junction structure of triple junction structure or more has a bottom cell and a top cell, And has at least one middle cell positioned therein.

Typically, the mother substrate for forming the compound semiconductor layer is formed of a GaAs single crystal wafer or a Ge single crystal wafer, and a GaAs single crystal wafer or a Ge single crystal wafer has a lattice constant of 5.65 angstroms.

Therefore, the compound semiconductor layer formed on the mother substrate has the same lattice constant as the mother substrate.

Therefore, in the compound semiconductor solar cell having a double junction structure, the compound semiconductor layer forming the bottom cell located on the rear electrode side has a lower band gap energy than the compound semiconductor layer forming the top cell located on the front electrode side For example, GaAs, and the compound semiconductor layer forming the top cell is formed of a material having a higher band gap energy than the bottom cell, for example, GaInP.

1 and 2, when a compound semiconductor layer having a double junction structure is grown on a GaAs single crystal wafer or a Ge single crystal wafer having 5.65 angstroms, the bottom cell has a base layer formed on the basis of GaAs or Ge , The band gap energy of the bottom cell has a band gap energy of 1.42 eV which is equal to the band gap energy of the base layer of the bottom cell.

And, since the top cell typically has a base layer formed on the basis of GaInP, the band gap energy of the top cell must have a band gap energy of 1.88 eV which is equal to the band gap energy of the base layer of the top cell.

In this case, referring to FIGS. 3 and 4, the theory of a double junction structure compound semiconductor solar cell including a bottom cell having a base layer formed on the basis of GaAs and a top cell having a base layer formed on the basis of GaInP The efficiency is limited to 34.9%.

3 and 4, since the maximum theoretical efficiency obtained in a compound semiconductor solar cell having a double junction structure is 37.5%, the theoretical efficiency of the compound semiconductor solar cell having the double junction structure is the same as the maximum theoretical efficiency There is a difference.

Therefore, there is a need for a method of increasing the theoretical efficiency of the double junction structure compound semiconductor solar cell to the maximum theoretical efficiency.

It is an object of the present invention to provide a mother board capable of manufacturing a high efficiency compound semiconductor solar cell close to maximum theoretical efficiency, a method of manufacturing a compound semiconductor solar cell using the mother board, and a high efficiency compound semiconductor solar cell.

A mother substrate according to one aspect of the present invention comprises a GaAs single crystal wafer or a Ge single crystal wafer; And a metamorphic layer in direct physical contact with one side of the GaAs single crystal wafer or the Ge single crystal wafer and having a lattice constant varying along the thickness direction.

The lattice constant of the first surface contacting the GaAs single crystal wafer or the Ge single crystal wafer is formed to be smaller than the lattice constant of the second surface located on the opposite side of the first surface from both surfaces of the modified layer, The lattice constant of the first surface may increase stepwise, exponentially or logarithmically from the first surface to the second surface.

The lattice constant on the first surface of the modified layer may be equal to the lattice constant of the GaAs single crystal wafer or the Ge single crystal wafer.

The GaAs single crystal wafer or the Ge single crystal wafer may have a lattice constant of 5.65 A and the modified layer may have a lattice constant of 5.70 A to 5.77 A larger than the lattice constant of the GaAs single crystal wafer or Ge single crystal wafer.

The modified layer having the above-mentioned lattice constant may be formed of In _x Ga _1-x P or In _x Ga _{1 -x} As, wherein x on the first surface is zero, X in the plane is 0.19.

Here, x means atomic% (atomic%).

The mother substrate may further include a sacrificial layer in direct physical contact with the second surface of the modified layer.

The sacrificial layer may have the same lattice constant as the GaAs single crystal wafer or the Ge single crystal wafer or may have the same lattice constant as the lattice constant on the second surface of the modified layer.

When the sacrificial layer has the same lattice constant as the GaAs single crystal wafer or the Ge single crystal wafer, the sacrifice layer is preferably formed to a thickness of 1 nm to 10 nm, and may be formed based on AlAs or AlGaAs.

Alternatively, if the sacrificial layer has a lattice constant equal to the lattice constant of the second surface of the modified layer, the sacrificial layer may be formed based on AlInAs or AlAsSb.

A compound semiconductor solar cell having such a configuration includes a step of forming a sacrificial layer on one side of a mother substrate; And forming a compound semiconductor layer for forming at least one cell on the sacrificial layer.

At this time, the mother substrate may be a GaAs single crystal wafer or a Ge single crystal wafer; And a metamorphic layer in direct physical contact with one side of the GaAs single crystal wafer or the Ge single crystal wafer and having a lattice constant varying along the thickness direction.

In the modified layer, the lattice constant of the first surface contacting the GaAs single crystal wafer or the Ge single crystal wafer from both surfaces of the modified layer is smaller than the lattice constant of the second surface located on the opposite side of the first surface . At this time, the lattice constant of the modified layer can be increased stepwise, exponentially or logarithmically from the first surface to the second surface.

The lattice constant on the first surface of the modified layer may be equal to the lattice constant of the GaAs single crystal wafer or the Ge single crystal wafer.

For example, the modified layer is In _x Ga _{1 -x} P or In _x Ga ₁ having a lattice constant of 5.70Å to 5.77Å _- can be formed as _x As. Where x means atomic%, x on the first side is zero, and x on the second side is 0.19.

The sacrificial layer may be formed to be in direct physical contact with the second surface of the modified layer, and may be formed based on AlAs or AlGaAs having the same lattice constant as the GaAs single crystal wafer or the Ge single crystal wafer, Can be formed based on AlInAs or AlAsSb having the same lattice constant as the lattice constant on the second surface.

When the sacrifice layer is formed on the GaAs single crystal wafer or the Ge single crystal wafer based on AlAs or AlGaAs having the same lattice constant as that of the GaAs monocrystalline wafer or the Ge single crystal wafer, in order to have the same lattice constant as that of the modified layer formed on the sacrifice layer, Layer is preferably formed to a thickness of 1 nm to 10 nm.

When forming the compound semiconductor layer, the base layer of the bottom cell may be formed of In _y Ga _{1 - y} As having a band gap energy of 0.95 eV to 1.20 eV and a lattice constant of 5.70 Å to 5.77 Å, Can be formed of Ga _z In _1-z P having a band gap energy of 1.60 eV to 1.80 eV and a lattice constant of 5.70 A to 5.77 A.

Here, y and z mean atomic%, y is 0.13 to 0.30, and z is 0.24 to 0.40.

The reason why y and z are limited to the above range is to satisfy the lattice constant of the compound semiconductor layer for effectively lowering the bandgap of each cell.

A back electrode having a sheet electrode shape may be formed on a back surface of the bottom cell and a grid electrode may be formed on a front surface of the top cell. .

A compound semiconductor solar cell having a multi junction structure of this structure, particularly a compound semiconductor solar cell having a double junction structure, has a band gap energy of 0.95 eV to 1.20 eV and a lattice constant of In _y Ga _{1 - y} As having a lattice constant of 5.70 Å to 5.77 Å A base layer of a bottom cell formed; A base layer of a top cell formed of Ga _z In _{1 - z} P having a band gap energy of 1.60 eV to 1.80 eV and a lattice constant of 5.70 A to 5.77 A; A rear electrode disposed on a back surface of the bottom cell and formed in the form of a sheet electrode; And a front electrode formed on a front surface of the top cell and formed in a grid shape.

Here, y is from 0.13 to 0.30, and z is from 0.24 to 0.40.

A mother substrate according to another aspect of the present invention comprises a GaAs single crystal wafer or a Ge single crystal wafer; A metamorphic layer formed of Ga _v In _{1 -v} P and located on one side of the GaAs single crystal wafer or the Ge single crystal wafer and having a lattice constant varying along the thickness direction; And a protective layer formed of In _w Ga _{1 - w} As and located on one side of the modified layer.

Here, v and w mean atomic%, respectively.

Wherein the lattice constant of the GaAs monocrystalline wafer or the Ge monocrystalline wafer on both sides of the modified layer is the same as the lattice constant of the GaAs single crystal wafer or the Ge single crystal wafer, The lattice constant on the second surface is greater than the lattice constant on the first surface and is equal to the lattice constant of the protective layer.

The lattice constant of the modified layer may increase stepwise, exponentially or logarithmically from the first surface to the second surface.

The GaAs single crystal wafer or the Ge single crystal wafer has a lattice constant of 5.65 A and the denaturing layer and the protective layer have a lattice constant of 5.70 A to 5.77 A larger than the lattice constant of the GaAs single crystal wafer or Ge single crystal wafer.

The modified layer on the first side is formed of Ga _0.52 In _0.48 P having a band gap energy of 1.60 to 1.80 eV, and v on the second side is 0.24 to 0.40.

In the protective layer, w is 0.13 to 0.30.

The mother substrate may further include a sacrificial layer located on the protective layer.

The sacrificial layer may have the same lattice constant as the GaAs single crystal wafer or the Ge single crystal wafer or may have the same lattice constant as the lattice constant on the second surface of the modified layer.

When the sacrificial layer has the same lattice constant as the GaAs single crystal wafer or the Ge single crystal wafer, the sacrifice layer is preferably formed to a thickness of 1 nm to 10 nm, and may be formed based on AlAs or AlGaAs.

Alternatively, if the sacrificial layer has a lattice constant equal to the lattice constant of the second surface of the modified layer, the sacrificial layer may be formed based on AlInAs or AlAsSb.

A compound semiconductor solar cell having such a configuration includes a step of forming a sacrificial layer on one side of a mother substrate; And forming a compound semiconductor layer for forming at least one cell on the sacrificial layer.

At this time, the mother substrate may be a GaAs single crystal wafer or a Ge single crystal wafer; A metamorphic layer formed of Ga _v In _{1 -v} P and located on one side of the GaAs single crystal wafer or the Ge single crystal wafer and having a lattice constant varying along the thickness direction; And In _w Ga _{1 - w} As, and may include a protective layer located on one side of the modified layer, and the first side contacting the GaAs single crystal wafer or the Ge single crystal wafer from both sides of the modified layer Wherein the lattice constant at the second surface located on the opposite side of the first surface is larger than the lattice constant at the first surface and the lattice constant at the second surface located at the opposite side of the first surface is larger than the lattice constant of the GaAs single crystal wafer or the Ge single crystal wafer, Lt; / RTI >

Here, v and w mean atomic%, respectively.

The lattice constant of the modified layer can be increased stepwise, exponentially or logarithmically from the first surface to the second surface.

The modified layer on the first side is formed of Ga _0.52 In _0.48 P having a band gap energy of 1.60 to 1.80 eV, and v on the second side is 0.24 to 0.40.

The sacrificial layer may be formed on the protective layer. The sacrificial layer may be formed on the GaAs single crystal wafer or the Ge single crystal wafer based on AlAs or AlGaAs having the same lattice constant, or may be formed on the second surface of the modified layer, Can be formed based on AlInAs or AlAsSb having the same lattice constant.

When the sacrifice layer is formed on the GaAs single crystal wafer or the Ge single crystal wafer based on AlAs or AlGaAs having the same lattice constant as that of the GaAs monocrystalline wafer or the Ge single crystal wafer, in order to have the same lattice constant as that of the modified layer formed on the sacrifice layer, Layer is preferably formed to a thickness of 1 nm to 10 nm.

According to the present invention, the mother substrate has a modified layer (and a protective layer for protecting the denatured layer) having an increased lattice constant as compared with a GaAs single crystal wafer or a Ge single crystal wafer, and the compound semiconductor layer is a denatured layer Lt; / RTI >

However, if the lattice constant increases, the band gap energy of the bottom cell and the top cell can be lowered as compared with the prior art.

That is, in the conventional double junction compound semiconductor solar cell having the same lattice constant as the GaAs single crystal wafer or the Ge cell single crystal wafer in the bottom cell and the top cell, the band gap energy of the bottom cell is 1.42 eV and the band gap energy of the top cell is 1.88 eV, the theoretical efficiency is limited to about 34.9%.

However, in the present invention, the band gap energy of the bottom cell can be reduced to 1.1 eV, and the band gap energy of the top cell can be reduced to 1.7 eV.

Accordingly, the bottom cell and the top cell of the compound semiconductor solar cell can be formed so as to have a band gap energy close to the maximum theoretical efficiency obtained in a compound semiconductor solar cell having a double junction structure.

Conventionally, a sacrificial layer is used to directly form a compound semiconductor layer on a GaAs single crystal wafer or a Ge single crystal wafer without separating the GaAs single crystal wafer or the Ge single crystal wafer from the compound semiconductor layer, thereby forming a modified layer between the compound semiconductor layers, The band gap energy may be adjusted by changing the lattice constant between the band gap energy and the band gap energy.

However, in this case, expensive GaAs single crystal wafers or Ge single crystal wafers can not be reused, and a modified layer in which a deposition time is longer than that of a compound semiconductor layer for forming a cell is formed every time a compound semiconductor solar cell is manufactured There is a problem to be done.

However, in the present invention, since the modified layer is formed directly on the GaAs single crystal wafer or the Ge single crystal wafer, and optionally the protective layer is formed directly on the modified layer, after the sacrificial layer is removed through the ELO (epitaxial lift off) Or the mother board comprising the denaturation layer and the protective layer can be reused.

Therefore, manufacturing cost can be reduced and formation time of the compound semiconductor layer can be reduced compared with the case where the lattice constant and the band gap energy are adjusted using the modified layer between the cell and the cell.

The mother substrate of the present invention can also be used for the production of a compound semiconductor solar cell having a multi-junction structure of triple junction structure or more including at least one middle cell.

FIG. 1 is a graph showing the correlation between the band gap energy and the lattice constant of various materials forming the compound semiconductor layer.

2 is a graph showing a correlation between band gap energies of a top cell and a bottom cell according to a lattice constant change.

3 is a graph showing the correlation between the lattice constant and the theoretical efficiency in three measurement environments.

4 is a graph showing the correlation between the magnitude of the band gap energy of the top cell and the bottom cell of the compound semiconductor solar cell used in the terrestrial environment and the theoretical efficiency.

FIG. 5 is a table showing changes in the band gap energy of the first light absorbing layer of the top cell and the band gap energy of the second light absorbing layer of the bottom cell according to the size of the lattice constant and the theoretical efficiency.

6 is a sectional view of a mother board according to the first embodiment of the present invention.

7 is a sectional view of a mother board according to a second embodiment of the present invention.

8 is a process diagram showing a method of manufacturing a compound semiconductor solar cell using the mother substrate shown in Fig.

9 is a sectional view of a mother board according to a third embodiment of the present invention.

10 is a sectional view of a mother board according to a fourth embodiment of the present invention.

11 is a process diagram showing a method for manufacturing a compound semiconductor solar cell using the mother substrate shown in Fig.

12 is a cross-sectional view of a compound semiconductor solar cell manufactured by the manufacturing method shown in Fig. 8 or Fig.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It is to be understood that the present invention is not intended to be limited to the specific embodiments but includes all changes, equivalents, and alternatives falling within the spirit and scope of the present invention.

In describing the present invention, the terms first, second, etc. may be used to describe various components, but the components may not be limited by the terms. The terms may only be used for the purpose of distinguishing one element from another.

For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

The term "and / or" may include any combination of a plurality of related listed items or any of a plurality of related listed items.

Where an element is referred to as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, but other elements may be present in between Can be understood.

On the other hand, when it is mentioned that an element is "directly connected" or "directly coupled" to another element, it can be understood that no other element exists in between.

The terminology used in this application is used only to describe a specific embodiment and is not intended to limit the invention. The singular expressions may include plural expressions unless the context clearly dictates otherwise.

In the present application, the terms "comprises", "having", and the like are used interchangeably to designate one or more of the features, numbers, steps, operations, elements, components, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, or combinations thereof.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. When a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the case directly above another portion but also the case where there is another portion in between. Conversely, when a part is "directly over" another part, it means that there is no other part in the middle.

Unless otherwise defined, all terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Terms such as those defined in commonly used dictionaries can be interpreted as having a meaning consistent with the meaning in the context of the relevant art and are, unless expressly defined in the present application, interpreted in an ideal or overly formal sense .

In addition, the following embodiments are provided to explain more fully to the average person skilled in the art. The shapes and sizes of the elements in the drawings and the like can be exaggerated for clarity.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a graph showing the correlation between the band gap energy and the lattice constant of various materials forming the compound semiconductor layer.

2 is a graph showing a correlation between band gap energies of a top cell and a bottom cell according to a lattice constant change.

3 is a graph showing the correlation between the lattice constant and the theoretical efficiency in three measurement environments.

4 is a graph showing the correlation between the magnitude of the band gap energy of the top cell and the bottom cell of the compound semiconductor solar cell used in the terrestrial environment and the theoretical efficiency.

FIG. 5 is a table showing changes in the band gap energy of the first light absorbing layer of the top cell and the band gap energy of the second light absorbing layer of the bottom cell according to the size of the lattice constant and the theoretical efficiency.

6 is a sectional view of a mother board according to the first embodiment of the present invention.

7 is a sectional view of a mother board according to a second embodiment of the present invention.

8 is a process diagram showing a method of manufacturing a compound semiconductor solar cell using the mother substrate shown in Fig.

9 is a sectional view of a mother board according to a third embodiment of the present invention.

10 is a sectional view of a mother board according to a fourth embodiment of the present invention.

11 is a process diagram showing a method for manufacturing a compound semiconductor solar cell using the mother substrate shown in Fig.

12 is a cross-sectional view of a compound semiconductor solar cell manufactured by the manufacturing method shown in Fig. 8 or Fig.

First, a compound semiconductor solar cell having a double junction structure compound semiconductor layer manufactured by the method for manufacturing a compound semiconductor solar cell using the mother substrate of the present invention will be described with reference to FIG.

The compound semiconductor solar cell having the double junction structure compound semiconductor layer includes a top cell C1, a grid-shaped front electrode 100 located on the front surface of the top cell C1, The first tunnel layer TRJ1 located between the top cell C1 and the bottom cell C2 and the first tunnel layer TRJ1 located between the top cell C1 and the bottom cell C2, and a rear electrode 200 having a sheet electrode shape.

At this time, the plurality of layers forming the top cell C1, the bottom cell C2 and the first tunnel layer TRJ1 are all formed of a compound semiconductor, and the front electrode 100 and the rear electrode 200 are formed of a conductive metal .

The top cell C1 includes a first light absorbing layer PV1, a first surface of the first light absorbing layer PV1, for example, a first window layer WD1 located on a front surface, And a first rear front layer BSF1 located on the second side of the first light absorbing layer PV1, for example, the rear side.

The first light absorbing layer PV1 includes a first base layer PV1-1 including an n-type impurity and in contact with the first window layer WD1, a first base layer PV1-1 including a p-type impurity, And a first emitter layer PV1-2 located on the rear surface of the first base layer PV1-1 and forming a pn junction with the first base layer PV1-1 and the first emitter layer PV1-1, 2) is formed of an indium phosphide (hereinafter referred to as InP) -based compound semiconductor.

As an example, the first base layer PV1-1 is formed of n-type Ga _z In _1-z P having a band gap energy of 1.60 eV to 1.80 eV and a lattice constant of 5.70 A to 5.77 A, (PV1-2) is formed of p-type Ga _z In _1-z P having a band gap energy of 1.60 eV to 1.80 eV and a lattice constant of 5.70 Å to 5.77 Å.

In this case, z is in the range of 0.24 to 0.40. The reason for limiting the range of z is to effectively reduce the bandgap of the top cell by effectively reducing the lattice constant of the top cell.

For example, the first base layer PV1-1 may be formed of n-type Ga _0.33 In _0.67 P having a band gap energy of 1.7 eV, and the first emitter layer PV1-2 may have a band gap energy of 1.7 eV _Lt; RTI ID = 0.0 > Ga _0.33 In _0.67 P. < / RTI >

The p-type impurity doped in the first emitter layer PV1-2 may be selected from carbon (C), magnesium (Mg), zinc (Zn), or a combination thereof. The doped n-type impurity may be selected from silicon (Si), selenium (Se), tellurium (Te), or a combination thereof.

Accordingly, a pn junction in which the first emitter layer PV1-2 and the first base layer PV1-1 are joined is formed in the first light-absorbing layer PV1, so that the first light- The electron-hole pairs generated by the light are separated into electrons and holes by the internal potential difference formed by the pn junction of the first light-absorbing layer PV1, the electrons move toward the n-type, and the holes move toward the p-type.

Therefore, the holes generated in the first light absorbing layer PV1 move to the rear electrode 200 through the bottom cell C2, and the electrons generated in the first light absorbing layer PV1 pass through the first window layer WD1, And moves to the front electrode 100 through the front contact layer FC.

Alternatively, when the positions of the first emitter layer PV1-2 and the first base layer PV1-1 are changed from each other, holes generated in the first light absorbing layer PV1 may be transmitted through the front contact layer FC The electrons generated in the first light absorbing layer PV1 move to the rear electrode 200 through the rear contact layer BC.

The first backside front layer BSF1 has the same conductivity type as the first emitter layer PV1-2 physically in direct contact and is made of an InP-based material similar to the first window layer WD1, For example, p-type AlInP.

As an example, the first backside front layer (BSF1) may be formed of p-type Al _0.67 In _0.33 P having a band gap energy of 2.2 eV and a lattice constant of 5.70 A to 5.77 A.

The first rear whole front layer BSF1 is formed of a first rear front layer BSF1 and a second rear front layer BSF2 which are physically in direct contact with each other in order to effectively block charges (holes or electrons) Is formed entirely on the back surface of the emitter layer PV1-2.

The first emitter layer PV1-2 and the first base layer PV1-1 can be made of the same material (homogeneous junction) having the same band gap energies and can be made of different materials having different band gap energies It can be made of other materials (heterojunction).

In the case of homojunction, the first base layer PV1-1 may be formed of n-type Ga _z In _1-z P having a band gap energy of 1.60 eV to 1.80 eV and a lattice constant of 5.70 A to 5.77 A, The first emitter layer PV1-2 may be formed of p-type Ga _z In _1-z P having a band gap energy of 1.60 eV to 1.80 eV and a lattice constant of 5.70 Å to 5.77 Å.

The first window layer WD1 may be formed between the first light absorbing layer PV1 and the front electrode 100 and may be formed by doping an n-type impurity into the III-VI group semiconductor compound.

However, when the first emitter layer PV1-2 is located on the first base layer PV1-1 and the first window layer WD1 is located on the first emitter layer PV1-2, WD1) may include a p-type impurity.

The first window layer WD1 functions to passivate the front surface of the first light absorbing layer PV1. Therefore, when carriers (electrons and holes) move to the surface of the first light absorbing layer PV1, the first window layer WD1 can prevent the carriers from recombining on the surface of the first light absorbing layer PV1.

In addition, since the first window layer WD1 is disposed on the front surface of the first light absorbing layer PV1, that is, on the light incident surface, the first light absorbing layer PV1 is formed on the first light absorbing layer PV1, It is necessary to have a band gap energy energy higher than the band gap energy energy of the first photovoltaic element PV1.

In addition, it is necessary to form the first window layer WD1 with a substance which is hardly dissolved in the ELO process using hydrofluoric acid.

Thus, for example, the first window layer WD1 may be formed of n-type Al _0.33 In _0.67 P having a band gap energy of 2.2 eV and a lattice constant of 5.70 A to 5.77 A.

The first rear whole layer BSF1 may be thicker than the first window layer WD1. As an example, the first rear whole layer BSF1 may be formed to a thickness of 50 to 100 nm.

The antireflection film (not shown) may be located in a region other than the region where the front electrode 100 and / or the front contact layer FC are located in the front surface of the first window layer WD1.

Alternatively, the antireflection film may be disposed on the front contact layer FC and the front electrode 100 as well as the first window layer WD1.

The antireflection film having such a configuration may include magnesium fluoride, zinc sulfide, titanium oxide, silicon oxide, derivatives thereof, or a combination thereof.

The compound semiconductor solar cell may further include a bus bar electrode physically connecting the plurality of front electrodes 100. The bus bar electrode may be exposed to the outside without being covered by the antireflection film.

The front electrode 100 may be formed to extend in the first direction and spaced apart at a predetermined interval along a second direction Y-Y 'orthogonal to the first direction.

The front electrode 100 having such a structure may be formed to include an electrically conductive material and may include at least one of gold (Au), germanium (Ge), and nickel (Ni), for example.

The front contact layer FC positioned between the first window layer WD1 and the front electrode 100 dopes the Group III-VI semiconductor compound with an n-type impurity at a doping concentration higher than that of the first base layer PV1-1 . As an example, the front contact layer (FC) may be formed of n + type In _0.19 Ga _0.81 As having a band gap energy of 1.1 eV and a lattice constant of 5.70 A to 5.77 A.

The front contact layer FC forms an ohmic contact between the first window layer WD1 and the front electrode 100. That is, when the front electrode 100 directly contacts the first window layer WD1, the impurity doping concentration of the first window layer WD1 is low, so that the gap between the front electrode 100 and the first light absorbing layer PV1 Ohmic contacts are not well formed.

Therefore, the carrier moved to the first window layer WD1 can not easily move to the front electrode 100 and can be destroyed.

However, when the front contact layer FC is formed between the front electrode 100 and the first window layer WD1, the movement of the carriers is prevented by the front contact layer FC forming the ohmic contact with the front electrode 100 So that the short circuit current density (Jsc) of the compound semiconductor solar cell increases. As a result, the efficiency of the solar cell can be further improved.

The front contact layer FC can be formed in the same plane shape as the front electrode 100.

Next, the bottom cell C2 and the first tunnel layer TRJ1 will be described.

The bottom cell C2 includes a second light absorbing layer PV2, a first surface of the second light absorbing layer PV2, for example, a second window layer WD2 located on the front surface, a second light absorbing layer PV2, A second backside front layer BSF2 located on a second side of the first back side layer BS2 and a rear side contact layer BC located on the back side of the second rear front side layer BSF2, .

The bottom cell C2 includes a light absorbing layer formed of a compound semiconductor including a second base layer and a second emitter layer based on GaAs.

As an example, the second base layer and the second emitter layer may be formed of In _y Ga _1-y As having a band gap energy of 0.95 eV to 1.20 eV and a lattice constant of 5.70 Å to 5.77 Å. Here, y is in the range of 0.13 to 0.30. The reason why _y is limited to the above range is to effectively reduce the band gap of the bottom cell by effectively reducing the lattice constant of In _y Ga _1-y As.

Specifically, the bottom cell C2 includes a second base layer PV2-1 formed of n-type In _0.19 Ga _0.81 As having a band gap energy of 1.1 eV and a lattice constant of 5.70 A to 5.77 A, (PV2-2) formed of p-type In _0.19 Ga _0.81 As having a band gap energy of 1.1 eV and a lattice constant of 5.70 A to 5.77 A, forming a pn junction with the first emitter layer (PV2-1) A second light absorbing layer PV2, an n-type Ga _0.33 layer having a band gap energy of 1.7 eV and a lattice constant of 5.70 A to 5.77 A, located between the first tunnel layer TRJ1 and the second base layer PV2-1, A second window layer WD2 formed of In _0.67 P and a p-type Ga _0.33 In layer having a band gap energy of 1.7 eV and a lattice constant of 5.70 A to 5.77 A, which are located on the back surface of the second emitter layer PV 2-2, _0.67 P in place between two layers around the rear (BSF2), and a second layer around the back (BSF2) and a back electrode 200 formed in and having a lattice constant of the 1.1eV band gap energy and 5.70Å to 5.77Å and a rear contact layer BC formed of p-type In _{0.1 9} Ga _0.81 As.

The bottom cell C2 is located at the rear of the top cell C1 to absorb light of long wavelength transmitted through the top cell C1 without being absorbed in the top cell C1.

Therefore, the second base layer PV2-1 and the second emitter layer PV2-2 form the first base layer PV1-1 and the first emitter layer PV1-2 of the top cell C1 A material having a band gap energy lower than the band gap energy of GaInP (approximately 1.9Ev), for example, InGaAs having a band gap energy of approximately 1.1 eV. For example, the second base layer PV2-1 and the second emitter layer PV2-2 may be formed of In _0.19 Ga _0.81 As having a band gap energy of 1.1 eV and a lattice constant of 5.70 A to 5.77 A, respectively have.

The second window layer WD2 and the second rear whole front side BSF2 are formed of a material having a higher band gap energy than the second base layer PV2-1 and the second emitter layer PV2-2, GaInP or AlGaInP. For example, the second window layer WD2 and the second rear whole layer BSF2 may be formed of Ga _0.33 In _0.67 P having a band gap energy of 1.7 eV and a lattice constant of 5.70 A to 5.77 A, respectively.

The first tunnel layer TRJ1 includes a first layer TRJ1 formed of p ++ type AlInGaAs doped with a higher concentration of p-type impurity than the first rear front layer BSF1 and physically in direct contact with the first rear front layer BSF1 And a second layer TRJ1-2 formed of n ++ -type GaInP doped with n-type impurity at a higher concentration than the second window layer WD2 and physically in direct contact with the second window layer WD2 can do.

For example, the first layer TRJ1-1 may be formed of p ++ type AlInGaAs (Al = 0.3) having a band gap energy of 1.6 eV and a lattice constant of 5.70 A to 5.77 A, and the second layer TRJ1-2 ) Can be formed of n ++ type GaInP (Ga = 0.33) having a band gap energy of 1.7 eV and a lattice constant of 5.70 A to 5.77 A.

The rear contact layer BC located on the rear surface of the first rear front layer BSF1 is entirely located on the rear surface of the first rear front layer BSF1 and is formed by doping a Group III- . As an example, the back contact layer BC may be formed of p + type In _0.19 Ga _0.81 As having a band gap energy of 1.1 eV and a lattice constant of 5.70 A to 5.77 A.

This rear contact layer BC can form an ohmic contact with the rear electrode 200, and the short circuit current density Jsc of the compound semiconductor solar cell can be further improved. As a result, the efficiency of the solar cell can be further improved.

The thickness of the front contact layer FC and the rear contact layer BC may each be formed to a thickness of 100 nm to 300 nm. In one example, the front contact layer FC may be formed to a thickness of 100 nm and the rear contact layer BC may be formed to a thickness of 300 nm.

The rear electrode 200 positioned on the rear surface of the rear contact layer BC may be formed as a sheet-like conductive material positioned entirely on the rear surface of the rear contact layer BC, unlike the front electrode 100 . That is, the rear electrode 200 may be referred to as a sheet electrode located on the entire rear surface of the rear contact layer BC.

At this time, the rear electrode 200 may be formed in the same plane as the first light absorbing layer PV1, and may be formed of various conductive materials.

For example, the rear electrode 200 includes a first electrode layer 200A that directly contacts a bottom layer of the bottom cell C2, for example, a rear surface of the rear contact layer BC to transmit a carrier, And a second electrode layer 200B positioned on the rear surface of the first electrode layer 200A to support the first electrode layer 200A.

At this time, the first electrode layer 200A for transmitting a carrier is formed of a material having a contact resistance similar to that of a conventional rear electrode forming material, that is, gold (Au), and is formed of a material having a high reflectivity can do.

Therefore, the first electrode layer 200A directly contacting the rear contact layer BC is formed of silver (Ag) having an excellent electrical bonding property with the rear contact layer BC and having an average reflectivity of 95% or more at a wavelength range of 600 nm to 950 nm ) May be formed by physical vapor deposition to a thickness of 50 to 500 nm.

The second electrode layer 200B that supports the first electrode layer 200A has a higher contact resistance than silver (Ag) that forms the first electrode layer 200B and has low reflectivity at a wavelength range of 600 nm to 950 nm. However, Copper (Cu) can be formed by electroplating to a thickness of 1 to 10 탆.

When the silver (Ag) having a low contact resistance with the rear contact layer BC and having a high average reflectivity in the wavelength range of 600 nm to 950 nm is used as the material for forming the first electrode layer 200A, And the photon recycling can be increased due to the reduction of the optical loss, so that the efficiency of the solar cell can be improved.

The compound semiconductor solar cell having such a structure can be manufactured by using any one of the mother board shown in Figs. 6, 7, 9 and 10.

Hereinafter, a method of manufacturing the compound semiconductor solar cell shown in Fig. 9 will be described with reference to Figs. 5 to 8. Fig.

Before describing a method of manufacturing a compound semiconductor solar cell, a mother board according to an embodiment of the present invention will be described first.

Fig. 6 shows the mother board of the first embodiment with the modified layer, and Fig. 7 shows the mother board of the second embodiment with the modified layer and the sacrificial layer.

And Fig. 9 shows a mother board of a third embodiment with a denatured layer and a protective layer, and Fig. 10 shows a mother board of the fourth embodiment with a denatured layer, a protective layer and a sacrificial layer.

The mother substrate 300-1, 300-2, 300-3, and 300-4 of the first to fourth embodiments may include a GaAs single crystal wafer or a Ge single crystal wafer, respectively. Hereinafter, the case where the mother substrate 300-1, 300-2, 300-3, and 300-4 includes the GaAs wafer 300A will be described as an example.

The mother substrate 300-1 of the first embodiment includes a GaAs wafer 300A and a metamorphic layer 300B that is in direct physical contact with one side of the GaAs wafer 300A.

The GaAs wafer 300A serves as a base layer for providing a plurality of compound semiconductor layers forming the bottom cell C2 and a plurality of compound semiconductor layers forming the top cell C1 to form a suitable lattice structure.

The modified layer 300A has a lattice constant of a plurality of compound semiconductor layers forming the bottom cell C2 and a lattice constant of a plurality of compound semiconductor layers forming the top cell C1 in comparison with the lattice constant of the GaAs wafer 300A Thereby adjusting the band gap energy of the bottom cell C2 and the band gap energy of the top cell C1 so as to obtain an efficiency close to the maximum theoretical efficiency obtained in a compound semiconductor solar cell having a double junction structure.

To obtain the above effect, the lattice constant of the modified layer 300B varies along the thickness direction. That is, the denatured layer 300B means a layer whose lattice constant varies along the thickness direction.

At this time, the lattice constant on the first surface contacting the GaAs wafer 300A on both sides of the modified layer 300B is equal to the lattice constant of the GaAs wafer 300A.

And the lattice constant of the modified layer 300B on the second surface located on the opposite side of the first surface may increase stepwise, exponentially or logarithmically from the first surface to the second surface.

The GaAs wafer 300A has a lattice constant of 5.65 ANGSTROM. Therefore, when the lattice constant of the compound semiconductor layer formed on the modified layer 300B is increased by the lattice constant of the GaAs wafer 300A using the modified layer 300B, the top cell and the bottom cell are formed directly on the GaAs wafer The band gap energy of the first light absorbing layer PV1 of the top cell C1 and the band gap energy of the second light absorbing layer PV2 of the bottom cell C2 can be lowered.

Referring to FIG. 5, when a bottom cell and a top cell are formed on a GaAs wafer having a lattice constant of 5.65 Å, Ga _{0 . 52} In _{0 .48} P a top cell (C1) and a first band gap energy is 1.88 of the light absorption layer (PV1), a bottom cell (C2) a second band gap of the light absorbing layer (PV2) to the formation of the GaAs to form a The energy is 1.42.

Therefore, the efficiency (AMO efficiency) when used in a space environment is 31.3%, the efficiency (AM1.5G efficiency) when used in a ground environment is 34.9% Is 32.5%.

However, when the modified layer 300B having the lattice constant increased to 5.7A on the second surface is formed on the GaAs wafer having the lattice constant of 5.65A and the bottom cell and the top cell are formed on the modified layer 300B Ga _{0 . 52} In _{0 .48} a top cell (C1) the first light absorbing layer a second light absorbing layer (PV2) of (PV1) a bottom cell (C2) formed in the band gap energy is lowered to 1.8, with the GaAs to form the P The band gap energy is reduced to 1.2.

Therefore, the efficiency (AMO efficiency) for use in a space environment is 33.8%, the efficiency for use in a ground environment (AM 1.5G efficiency) is 36.9% Is 33.6%.

When the modified layer 300B having the lattice constant increased to 5.73A on the second surface is formed on the GaAs wafer having the lattice constant of 5.65A and the bottom cell and the top cell are formed on the modified layer 300B Ga _{0 . 52} In _{0 .48} a top cell (C1) the first light absorbing layer a second light absorbing layer (PV2) of (PV1) a bottom cell (C2) formed in the band gap energy is lowered to 1.72, with the GaAs to form the P The band gap energy is lowered to 1.09.

Therefore, the efficiency (AMO efficiency) when used in a space environment is 34.2%, the efficiency (AM1.5G efficiency) when used in a ground environment is 37.1% Is 34.2%.

When the modified layer 300B having the lattice constant increased to 5.75A on the second surface is formed on the GaAs wafer having the lattice constant of 5.65A and the bottom cell and the top cell are formed on the modified layer 300B Ga _{0 . 52} In _{0 .48} a top cell (C1) the first light absorbing layer a second light absorbing layer (PV2) of (PV1) a bottom cell (C2) formed in the band gap energy is lowered to 1.66, with the GaAs to form the P The band gap energy is lowered to 1.03.

Accordingly, the efficiency (AMO efficiency) in the space environment is 33.9%, the efficiency (AM1.5G efficiency) in the use in the ground environment is 36.6%, the efficiency (AM1.5D efficiency) Is 34.8%.

Then, when the modified layer 300B having the lattice constant increased to 5.76A on the second surface is formed on the GaAs wafer having the lattice constant of 5.65A and the bottom cell and the top cell are formed on the modified layer 300B Ga _{0 . 52} In _{0 .48} a top cell (C1) the first light absorbing layer a second light absorbing layer (PV2) of (PV1) a bottom cell (C2) formed in the band gap energy is lowered to 1.63, with the GaAs to form the P The band gap energy is lowered to 1.09.

Therefore, the efficiency (AMO efficiency) when used in a space environment is 33.5%, the efficiency (AM1.5G efficiency) when used in a ground environment is 36.3% Is 35.1%.

According to the above, the AMO efficiency and AM1.5G efficiency are the highest when using a dense layer having a lattice constant of 5.73Å on the second side, and the AM1.5D efficiency is a lattice constant of 5.76Å on the second side The highest value is obtained in the case of using the modified layer having a high refractive index.

Therefore, a double-junction solar cell can be manufactured by appropriately selecting a modified layer having a lattice constant of 5.7 A to 5.77 A on the second surface in accordance with the use environment of the solar cell.

According to experiments of the present inventors, In _x Ga _{1 -x} P or In _x Ga _{1 -} in the modified layer (300B) formed by _x As, to the lattice constant of the second surface of the modified layer (300B) 5.70Å And the size of x for forming 5.77A was 0.19.

Therefore, x on the first surface of the modified layer 300B is 0 (zero), and x on the second surface is 0.19.

The modified layer 300B may be formed to a thickness of 200 to 300 nm and may be formed of a plurality of films within the thickness range to increase the lattice constant from the first surface to the second surface.

Hereinafter, a method of manufacturing a compound semiconductor solar cell using the mother substrate 300-1 of the first embodiment will be described.

A sacrificial layer 400 physically in direct contact with the modified layer 300B of the mother substrate 300-1 is formed on one surface of the modified layer 300B and the bottom cell C2 is formed on the sacrificial layer 400. [ A compound semiconductor layer CS3 for forming the first tunnel layer TRJ1 and a compound semiconductor layer CS1 for forming the top cell C1 are sequentially formed.

The sacrificial layer 400 may be formed of AlAs or AlAsSb having the same lattice constant as the lattice constant of the second surface of the modified layer 300B or may be formed of AlAs or AlGaAs having the same lattice constant as the GaAs wafer 300A, can do.

When the sacrificial layer 400 has a lattice constant equal to the lattice constant of the second surface of the modified layer 300B, the compound semiconductor layer of the bottom cell C2 formed on the sacrificial layer 400 and the compound semiconductor layer of the top cell C1 ) Has the same lattice constant as that of the modified layer 300B, so there is no particular limitation in forming the sacrifice layer. In this case, the sacrifice layer 400 may be formed to a thickness of 20 to 50 nm.

However, when the sacrifice layer 400 is formed on the basis of the AlAs or AlGaAs having the same lattice constant as the GaAs wafer 300A, the compound semiconductor layer formed on the sacrifice layer 400 is formed in the same lattice as the denatured layer 300B In order to have a constant, the thickness of the sacrificial layer 400 must be very thin.

According to the experiment of the present invention, when the sacrifice layer 400 is formed to a thickness of 1 nm to 10 nm, the sacrifice layer 400 is formed on the basis of AlAs or AlGaAs having the same lattice constant as the GaAs wafer 300A The compound semiconductor layer of the bottom cell C2 and the compound semiconductor layer of the top cell C1 have the same lattice constant as the lattice constant of the second surface of the modified layer 300B.

Therefore, when forming the sacrificial layer 400 based on AlAs or AlGaAs having the same lattice constant as that of the GaAs wafer 300A, the sacrifice layer 400 is preferably formed to a thickness of 1 to 10 nm.

The compound semiconductor layer formed on the sacrificial layer 400 may be formed by a metal organic chemical vapor deposition (MOCVD) method, a molecular beam epitaxy (MBE) method, or any other suitable method for forming an epitaxial layer, And may be formed by a regular growth method or an inverse growth method.

After the compound semiconductor layer is formed, the sacrificial layer is removed by the ELF (epitaxial lift off) method using hydrofluoric acid (HF), so that the mother substrate 300-1 can be separated from the compound semiconductor layer.

In the first embodiment shown in Fig. 6, the case where the mother substrate 300-1 is formed of the GaAs wafer 300A and the modified layer 300B has been described.

However, the mother board of the present invention can be modified into various forms.

7, the mother substrate 300-2 may be formed of a GaAs wafer 300A-2, a denatured layer 300B, and a sacrificial layer 400. As shown in FIG.

The modified layer 300 and the sacrificial layer 400 provided on the mother substrate of the second embodiment of the present embodiment are the same as those described in the first embodiment.

9, the mother substrate 300-3 of the third embodiment includes a GaAs wafer 300A, a modified layer 300B-3 located on one side of the GaAs wafer 300A, And a protective layer 300C-3 located on one side of the modified layer 300B-3.

The modified layer 300B-3 is formed by lattice constants of a plurality of compound semiconductor layers forming the bottom cell C2 and lattice constants of a plurality of compound semiconductor layers forming the top cell C1 to a lattice constant of the GaAs wafer 300A The bandgap energy of the bottom cell C2 and the bandgap energy of the top cell C1 are adjusted so as to obtain an efficiency close to the maximum theoretical efficiency obtained in the compound semiconductor solar cell having the double junction structure.

In order to obtain the above effect, the lattice constant of the modified layer 300B-3 varies along the thickness direction.

That is, the lattice constant of the first surface in contact with the GaAs wafer 300A on both sides of the modified layer 300B-3 is equal to the lattice constant of the GaAs wafer 300A, and the lattice constant of the first surface contacting the protective layer 300C- The lattice constant on the second surface is the same as the lattice constant of the protective layer 300C-3.

In the modified layer 300B-3, the atomic% of Ga may decrease stepwise, exponentially or logarithmically from the first surface to the second surface. Therefore, the lattice constant of the modified layer 300B-3 may increase stepwise, exponentially or logarithmically from the first surface to the second surface.

The modified layer 300B-3 of this embodiment is formed of Ga _v In _{1 -v} P, and the size of v for forming the lattice constant of the second surface of the modified layer 300B-3 from 5.70A to 5.77A Is in the range of 0.24 to 0.40, and the modified layer (300B-3) has a band gap energy of 1.60 to 1.80 eV.

Therefore, the modified layer 300B-3 on the first surface is made of Ga _{0 . 52} In _{0 .48} P, and the modified layer 300 B on the second surface is formed of Ga _v In _{1 -v} P (v = 0.24 to 0.40).

The modified layer 300B-3 may be formed to a thickness of 200 to 300 nm, and may be formed of a plurality of films within the thickness range to increase the lattice constant from the first surface to the second surface.

The protective layer (300C-3) is formed on the modified layer (300B-3) to protect the modified layer (300B-3) in the ELO process, In _w Ga _{1 -} it is formed of a single layer formed of a _w As. The protective layer 300C-3 has a band gap energy of 0.95 to 1.20 eV, and the protective layer 300C-3 has a band gap energy of 0.95 to 1.20 eV, with w having a lattice constant of 5.70 A to 5.77 A of 0.13 to 0.30.

A method of manufacturing a compound semiconductor solar cell using a mother substrate 300-3 including a modified layer 300B-3 formed on a GaAs wafer 300A and a protective layer 300C-3 will be described below.

A compound semiconductor layer CS2 forming a sacrificial layer 400 on the protective layer 300C-3 of the mother substrate 300-3 and forming a bottom cell C2 on the sacrificial layer 400, The compound semiconductor layer CS3 for forming the first tunnel layer TRJ1 and the compound semiconductor layer CS1 for forming the top cell C1 are sequentially formed.

The sacrificial layer 400 may be made of AlAs or AlGaAs having the same lattice constant as the GaAs wafer 300A or AlInAs or AlAsSb having the same lattice constant as the lattice constant of the protective layer 300C-3 .

When the sacrifice layer 400 has a lattice constant equal to the lattice constant of the protective layer 300C-3, the compound semiconductor layer of the bottom cell C2 formed on the sacrifice layer 400 and the compound of the top cell C1 Since the semiconductor layer also has the same lattice constant as the protective layer 300C-3, there is no particular limitation in forming the sacrificial layer. In this case, the sacrifice layer 400 may be formed to a thickness of 20 to 50 nm.

However, when the sacrifice layer 400 is formed on the basis of AlAs or AlGaAs having the same lattice constant as the GaAs wafer 300A, the compound semiconductor layer formed on the sacrifice layer 400 is formed on the protective layer 300C- In order to have the same lattice constant, the thickness of the sacrificial layer 400 should be very thin.

According to the experiment of the present invention, when the sacrifice layer 400 is formed to a thickness of 1 nm to 10 nm, the sacrifice layer 400 is formed on the basis of AlAs or AlGaAs having the same lattice constant as the GaAs wafer 300A The compound semiconductor layer of the bottom cell C2 and the compound semiconductor layer of the top cell C1 have the same lattice constant as the lattice constant of the protective layer 300C-3.

Therefore, when forming the sacrificial layer 400 based on AlAs or AlGaAs having the same lattice constant as that of the GaAs wafer 300A, the sacrifice layer 400 is preferably formed to a thickness of 1 to 10 nm.

After the compound semiconductor layer is formed on the sacrificial layer 400, the sacrificial layer is removed by the ELF (epitaxial lift off) method using hydrofluoric acid (HF), so that the mother substrate 300-3 can be separated from the compound semiconductor layer After the sacrificial layer is removed, the protective layer 300C-3 for protecting the denatured layer 300B-3 in the ELO process is removed by using NH ₄ OH / H ₂ O ₂ / DI water, H ₃ PO ₄ / H ₂ O ₂ / DI water, H ₂ SO ₄ / H ₂ O ₂ / DI water, or a mixture thereof. Alternatively, the protective layer 300C-3 may not be removed.

9, the case where the mother substrate 300-3 is formed of the GaAs wafer 300A, the modified layer 300B-3, and the protective layer 300C-3 has been described. However, as shown in FIG. 10 And the mother substrate 300-4 may be formed of the GaAs wafer 300A, the denatured layer 300B-4, the protective layer 300C-4, and the sacrificial layer 400. [

Although the compound semiconductor solar cell having a double junction structure is described above as an example, it is obvious that the manufacturing method of the present invention can also be used in manufacturing a compound semiconductor solar cell having a compound semiconductor layer having a triple junction or more structure.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

Claims (18)

1. GaAs single crystal wafer or Ge single crystal wafer; And

   A metamorphic layer directly contacting the one side of the GaAs single crystal wafer or the Ge single crystal wafer and having a lattice constant varying along the thickness direction,

   A mosquito board comprising.
2. The method of claim 1,

   Wherein the lattice constant of the first surface contacting the GaAs single crystal wafer or the Ge single crystal wafer on both sides of the modified layer is smaller than the lattice constant of the second surface located on the opposite side of the first surface.
3. 3. The method of claim 2,

   Wherein the lattice constant of the modified layer increases stepwise, exponentially or logarithmically from the first surface to the second surface.
4. 4. The method according to any one of claims 1 to 3,

   Wherein the GaAs monocrystalline wafer or Ge monocrystalline wafer has a lattice constant of 5.65A and the denaturation layer has a lattice constant of 5.70A to 5.77A larger than the lattice constant of the GaAs single crystal wafer or the Ge single crystal wafer.
5. 5. The method of claim 4,

   Wherein the modified layer is formed of In _x Ga _1-x P or In _x Ga _{1 -x} As, wherein x on the first surface is zero and the x on the second surface is 0.19 plate.
6. The method of claim 5,

   And a sacrificial layer in direct physical contact with the second surface of the modified layer.
7. The method of claim 6,

   Wherein the sacrificial layer has a lattice constant equal to that of the GaAs single crystal wafer or the Ge single crystal wafer and is formed on the basis of AlAs or AlGaAs and formed to a thickness of 1 nm to 10 nm.
8. The method of claim 6,

   Wherein the sacrificial layer has a lattice constant equal to the lattice constant on the second surface of the modified layer and is formed based on AlInAs or AlAsSb.
9. 5. The method of claim 4,

   The modified layer is a Ga _1-v In _v is formed from a P, the modified layer in the first surface having a Ga ₀ of 1.60 to 1.80eV bandgap _{energy. 52} In _{0 .48} P, and v in said second side is 0.24 to 0.40.
10. The method of claim 9,

    Further comprising a protective layer located on one side of the modified layer and formed of In _w Ga _1-w As,

    Wherein the lattice constant of the GaAs monocrystalline wafer or the Ge monocrystalline wafer on both sides of the modified layer is the same as the lattice constant of the GaAs single crystal wafer or Ge single crystal wafer, And a lattice constant greater than the lattice constant at the first surface and equal to the lattice constant of the protective layer.
11. 11. The method of claim 10,

    Wherein the protective layer has a lattice constant of 5.70 A to 5.77 A greater than the lattice constant of the GaAs single crystal wafer or Ge single crystal wafer.
12. 11. The method of claim 10,

    Wherein, in the protective layer, w is 0.13 to 0.30.
13. The method of claim 12,

    And a sacrificial layer disposed over the protective layer.
14. The method of claim 13,

    Wherein the sacrificial layer has a lattice constant equal to that of the GaAs single crystal wafer or the Ge single crystal wafer and is formed on the basis of AlAs or AlGaAs and formed to a thickness of 1 nm to 10 nm.
15. The method of claim 13,

    Wherein the sacrificial layer has a lattice constant equal to the lattice constant of the protective layer and is formed based on AlInAs or AlAsSb.
16. Forming a sacrificial layer on one side of the mother substrate; And

    Forming a compound semiconductor layer for forming one or more cells on the sacrificial layer

    / RTI >

    The mosquito-

    GaAs single crystal wafer or Ge single crystal wafer; And

    A metamorphic layer directly contacting the one side of the GaAs single crystal wafer or the Ge single crystal wafer and having a lattice constant varying along the thickness direction,

    Wherein the method comprises the steps of:
17. 17. The method of claim 16,

    Wherein the mother substrate further comprises a protective layer located on one side of the modified layer and physically in direct contact with one side of the sacrificial layer.
18. A compound semiconductor solar cell having a multi-junction structure,

    A base layer of a bottom cell formed of In _y Ga _1-y As having a band gap energy of 0.95 eV to 1.20 eV and a lattice constant of 5.70 A to 5.77 A;

    A base layer of a top cell formed of Ga _z In _1-z P having a band gap energy of 1.60 eV to 1.80 eV and a lattice constant of 5.70 A to 5.77 A;

    A rear electrode disposed on a back surface of the bottom cell and formed in the form of a sheet electrode; And

    A front electrode disposed on a front surface of the top cell and formed in a grid shape,

    / RTI >

    Y is from 0.13 to 0.30, and z is from 0.24 to 0.40.

Images