KR20110082886A - High efficiency semiconductor photo device of epitaxial structure and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A high efficient semiconductor optical device formed by an epitaxial structure and a manufacturing method thereof are provided to insert diffusion preventing layers into the upper/lower parts of each barrier layer of an MWQ(Multi-Quantum Well) structure, thereby increasing quantum efficiency. CONSTITUTION: An active layer(30) is formed on an N type nitride semiconductor layer(20). An electron blocking layer(40) is formed on the active layer. A P type nitride semiconductor layer(50) is formed on the electron blocking layer. The transparent conductive film(52) is formed on the P-type nitride semiconductor layer. The P-type contact metal electrode(54) is formed on the transparent conductive film.

Description

High efficiency semiconductor photo device formed of epitaxial structure and its manufacturing method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor optical device, and more particularly, to a structure having a barrier layer in which a P-type or N-type dopant is selectively doped in a multi-quantum well (MQW) structure of an active layer, and top and bottom of each barrier layer. A quantum efficiency can be improved by applying a diffusion blocking layer (DBL) to prevent diffusion of dopants to semiconductor optical devices such as light emitting diodes (LEDs), laser diodes, photodetectors or solar cells. The present invention relates to a semiconductor optical device and a method of manufacturing the same.

Semiconductor optical devices such as light emitting diodes (LEDs), laser diodes, photodetecting devices, or solar cells have a basic structure in which an active layer is bonded between a P-type semiconductor layer and an N-type semiconductor layer, and when a forward voltage is applied, electrons excited in the active layer Operates on the principle of emitting light by recombination.

Such light emitting diodes (LEDs) are used as light emitting lamps for various electronic devices such as automobile dashboards, taillights, keyboards, traffic lights and LCD backlights, and laser diodes and photodetecting devices are used for equipment for spectrum analysis and human diagnosis. Various applications have been made in the industry, and researches to increase the efficiency of solar cells used in power generation facilities for producing renewable energy have been actively conducted in recent years.

In a semiconductor optical device such as a general light emitting diode, a multi-quantum well (MQW) structure is applied to an active layer to improve quantum efficiency. However, since a simple MQW structure has a limitation in improving quantum efficiency, many studies have been conducted on MQWs having various structures.

The present invention intends to propose an optical device structure and a method of manufacturing the same that can improve the performance of the optical device by increasing the quantum efficiency by varying the structure for the MQW.

Accordingly, an object of the present invention is to solve the above problems, and an object of the present invention is to improve the quantum efficiency with a structure having a barrier layer selectively doped with a P-type or N-type dopant in the MWQ structure of the active layer. The present invention provides a semiconductor optical device and a method of manufacturing the same.

In addition, by providing a diffusion barrier layer (DBL) to prevent the diffusion of the dopant in the upper and lower barrier layers of the MWQ structure to provide a semiconductor optical device that can further improve the quantum efficiency and the performance of the optical device and a method of manufacturing the same There is.

First, to summarize the features of the present invention, a method for manufacturing a semiconductor device according to an aspect of the present invention for achieving the above object of the present invention, the active layer and the electron between the N-type compound semiconductor layer and the P-type compound semiconductor layer A method of manufacturing a semiconductor device, which forms an optical device structure having a blocking layer (EBL), wherein the active layer includes a multi-quantum well (MQW) layer structure, and the forming of the MQW layer may include forming a barrier layer. A first process, a second process of forming a well layer on the barrier layer, and a third process of forming a barrier layer on the well layer, and a barrier layer below the well layer or a barrier layer on the well layer. Doped with the predetermined dopant.

In the semiconductor device manufactured by the above manufacturing method, a fourth process of forming a diffusion barrier layer (DBL) below the barrier layer before forming the barrier layer below the well layer or the barrier layer above the well layer; The method may further include a fifth process of forming a barrier layer under the well layer or a barrier layer over the well layer, and then forming a diffusion barrier layer DBL on the barrier layer.

The diffusion barrier layer (DBL) is an Al _x In _y Ga _{1 -x- y} N (0 <x <1, 0 <y <1) nitride semiconductor layer having a lower dopant concentration or a different composition ratio than the barrier layer or the well layer. Can be made.

And a structure in which the formation of the well layer and the formation of the barrier layer are sequentially repeated a plurality of times on the barrier layer formed by the first process.

The well layer is formed on the diffusion barrier layer DBL formed by the fourth process, the barrier layer formed by the first process, and the diffusion barrier layer DBL formed by the fifth process, and the diffusion barrier layer DBL is formed. And a structure in which the formation of the barrier layer and the formation of the diffusion barrier layer (DBL) are sequentially repeated a plurality of times.

In the repeated structure, the barrier layer under the intermediate well layer is doped with an N-type dopant, and the barrier layer over the intermediate well layer is doped with a P-type dopant.

The N-type compound semiconductor layer is an In _x Ga _{1 -x} N (0 <x <1) nitride semiconductor layer doped with an N-type dopant, and the P-type compound semiconductor layer is In _x Ga _{1 -} doped with a P-type dopant. _x N (0 <x <1) nitride semiconductor layer.

The N-type dopant is any one of Si, Ge, or Sn, and the P-type dopant is any one of Mg, Zn, Cd, Be, Ca, or Ba.

The barrier layer and the well layer is _{-x- y Al x In y Ga 1} N (0 <x <1, 0 <y <1) is a nitride semiconductor layer.

According to the semiconductor optical device and the manufacturing method thereof according to the present invention, the quantum efficiency can be improved by a structure having a barrier layer selectively doped with a P-type or N-type dopant in the MWQ structure of the active layer, and each barrier of the MWQ structure Inserting a diffusion barrier layer (DBL) to prevent the diffusion of the dopant in the upper and lower layers, it is possible to further improve the quantum efficiency and the performance of the optical device.

1 is a cross-sectional view illustrating a semiconductor device in accordance with an embodiment of the present invention.
FIG. 2 is a comparison graph of internal quantum efficiency and forward voltage of the structure of FIG. 1 and the existing structure.
3 is a comparison graph of the light intensity of the structure of FIG. 1 and the existing structure.
Figure 4 is a graph of the emission intensity for the MQW structure based on the existing InGaN well layer and GaN barrier layer.
FIG. 5 is a graph showing emission intensity of the MQW structure based on the conventional InGaN well layer and the InGaN barrier layer.
FIG. 6 is a graph of luminescence intensity for an MQW structure based on an InGaN well layer and an InGaN barrier layer selectively doped according to an embodiment of the present invention.
FIG. 7 is a graph for comparing and explaining an internal quantum efficiency with respect to a current for each barrier type.
8 is a view for explaining dopant diffusion between the well layer and the barrier layer.
9 is a cross-sectional view illustrating a semiconductor device in accordance with another embodiment of the present invention.
FIG. 10 is a band diagram for explaining the role of the diffusion barrier layer in the structure of FIG. 9.
FIG. 11 is a graph of XRD intensity for each thickness of the diffusion barrier layer of the structure of FIG. 9.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. Like reference numerals in the drawings denote like elements.

1 is a cross-sectional view illustrating a semiconductor device 100 in accordance with an embodiment of the present invention.

Referring to FIG. 1, a semiconductor device 100 according to an embodiment of the present invention may include an N-type nitride semiconductor layer 20 and a barrier layer, which is a compound semiconductor GaN layer (about 2 micrometers) doped with an N-type dopant. 7.5 nanometer level and the well layer of 2.5-nm or so) the number of times (five times), repeat the MQW (multi quantum well) active layer one _{(30), Al 0 .12 Ga} 0 .88 N layer (20, formed of a structure Epitaxially an electron blocking layer (EBL) 40 which is about nanometers) and a P-type nitride semiconductor layer 50 which is a compound semiconductor GaN layer (about 100 nanometers) doped with a P-type dopant It has a structure laminated in order by the structure.

In addition, a transparent conductive film (ITO: In Tin Oxide) 52 is formed on the P-type nitride semiconductor layer 50. Subsequently, in order to form an electrode for electrical connection between the transparent conductive film 52 and the N-type nitride semiconductor layer 20, first, by etching a required portion through a predetermined mask exposure operation, a metal material is deposited to deposit the transparent conductive film 52. The P-type contact metal electrode 54 is formed to a thickness of about 110 nanometers in a portion of the upper portion, and the N-type contact metal electrode 22 is 110 nanometers in a portion of the N-type nitride semiconductor layer 20. It should be formed to a thickness of about a meter. The P-type contact metal electrode 54 and the N-type contact metal electrode 22 may be made of a metal material such as Ni, Au, or an alloy thereof.

Above, the electron blocking layer 40 for blocking the spread of the electrons generated in the active layer 30, but is heard as an example a layer Al _{0 .12} Ga _{0 .88} N, not limited to this, Al _x Ga _{1- As in x} N (0 <x <1), the ratio of Al and Ga may be different. The electron blocking layer 40 may be doped with a dopant concentration of about 5 * 10 ¹⁹ using a P-type dopant (Mg, etc.).

In addition, the semiconductor device 100 is a device structure based on a group 3-5 compound semiconductor (or nitride semiconductor), the N-type dopant mentioned in the present invention may be Si, Ge, Sn, etc., P-type dopant May be Mg, Zn, Cd, Be, Ca and Ba and the like.

Particularly, in the present invention, the quantum efficiency can be improved by a structure having a barrier layer selectively doped with a P-type or N-type dopant in the MWQ structure of the active layer 30. In addition, in order to further improve the quantum efficiency and the performance of the optical device, a structure in which a diffusion barrier layer (DBL) is inserted to prevent diffusion of dopants above and below each barrier layer of the MWQ structure will be described in FIG. 9. .

First, the process of forming the MQW layer of the active layer 30 is as follows. As shown in FIG. 1 or FIG. 10, the process of forming the active layer 30 includes forming a barrier layer on the N-type nitride semiconductor layer 20 and sequentially stacking a well layer and a barrier layer thereon. That is, the active layer 30 has a structure in which a barrier layer is formed on the N-type nitride semiconductor layer 20, and the formation of the well layer and the formation of the barrier layer are sequentially repeated a plurality of times (for example, five times). Can be formed.

Wherein each well layer and each barrier layer constituting the active layer 30 may be formed of a Ga _{0 .85 0 .15} In N, however, not limited to _{this, In x Ga 1 -x N (} 0 <x < As in 1), the ratio of In and Ga may be different. In addition, each well layer and each barrier layer may be an Al _x In _y Ga _{1- xy} N (0 <x <1, 0 <y <1) nitride semiconductor layer. In particular, any kind of well layer (s) and barrier layer (s) constituting the active layer 30 may be selectively doped with a predetermined dopant (N-type or P-type dopant). For example, the lower barrier layer of the well layer may be doped with an N type dopant, and the upper barrier layer of the well layer may be doped with a P type dopant.

In particular, in the structure in which the barrier layer is formed on the N-type nitride semiconductor layer 20 and then the formation of the well layer and the formation of the barrier layer are sequentially repeated a plurality of times, the barrier layer (s) under the intermediate well layer is Doped with an N-type dopant, the barrier layer (s) on top of the intermediate well layer may be doped with a P-type dopant. For example, as shown in FIG. 10, in the structure in which the barrier layer is formed on the N-type nitride semiconductor layer 20, and then the formation of the well layer and the formation of the barrier layer are sequentially repeated five times, the middle third well Based on the layer, the barrier layer (s) below it may be doped with an N-type dopant, and the barrier layer (s) above the third well layer may be doped with a P-type dopant. As described above, the N-type dopant may be Si, Ge, Sn, and the like, and the P-type dopant may be Mg, Zn, Cd, Be, Ca, and Ba, and the like. Each dopant may be doped into each layer at a predetermined amount of dopant, for example, a dopant concentration of about 1 * 10 ¹⁹ .

When comparing the internal quantum efficiency (IQE) and the forward voltage (Vf) of the semiconductor device (for example, a light emitting diode) of the structure as shown in FIG. 1 according to an embodiment of the present invention with other conventional structures same.

As shown in FIG. 2, in the MQW structure shown in FIG. 1 (half doped InGaN in FIG. 2), a first existing structure (GaN in FIG. 2) in which GaN is formed as a barrier layer or a second existing structure in which the barrier layer is not doped (FIG. It can be seen that the internal quantum efficiency IQE is increased and the forward voltage Vf is decreased than u-InGaN of 2. In the first existing structure (GaN of FIG. 2) and the second existing structure (u-InGaN of FIG. 2), an InGaN layer was used as the well layer.

In addition, as shown in FIG. 3, in the MQW structure (Half doped InGaN of FIG. 3) according to the exemplary embodiment of the present invention, the first existing structure (GaN of FIG. 3) or the barrier layer in which GaN is formed as a barrier layer is not doped. It can be seen that the emission intensity is higher than that of the second existing structure (u-InGaN of FIG. 3).

4 is a graph of emission intensity of the MQW structure (first existing structure) based on the existing InGaN well layer and the GaN barrier layer. FIG. 5 is a graph showing light emission intensity of a conventional InGaN well layer and an InGaN barrier layer-based MQW structure (second existing structure). FIG. 6 is a graph of luminescence intensity for an MQW structure (structure of the present invention) based on an InGaN well layer and an InGaN barrier layer selectively doped in accordance with an embodiment of the present invention. As can be seen in comparison with FIGS. 4, 5, and 6, in the structure in which the well layer is repeated 1 to 5 times, the emission intensity (FIG. 6) according to the structure of the present invention is the first existing structure (FIG. 4) or It can be seen that much higher than in the second existing structure (FIG. 5).

FIG. 7 is a graph for comparing and explaining an internal quantum efficiency with respect to a current for each barrier type (the existing first and second structures and the structure of the present invention). As shown in FIG. 7, when the forward voltage is applied to the metal electrodes 22 and 54 and the internal quantum efficiency IQE is compared with respect to the current, the MWW structure (Half doped InGaN of FIG. 7) according to the exemplary embodiment of the present invention is used. The internal quantum efficiency in the current range of 0 to 1000 A / cm ² is greater than that of the first conventional structure in which GaN is formed as a barrier layer (GaN in FIG. 7) or the second conventional structure in which the barrier layer is not doped (u-InGaN in FIG. 7). IQE) is much higher.

Meanwhile, the quantum efficiency can be further improved by improving the MQW structure of FIG. 1. As shown in FIG. 8, the dopants of the upper and lower barrier layers of the well layer constituting the MQW show a phenomenon that the dopant is diffused into the well layer during the formation of each layer. For example, when forming the well layer after forming the N-type barrier layer (N-type Al _x Ga _{1 - x} N layer), the N-type dopant may diffuse into the well layer to reduce the doping effect, and also, the well layer When the P-type barrier layer (P-type Al _x Ga _1-x N layer) is formed, the P-type dopant is diffused into the well layer to reduce the doping effect. FIG. 8 illustrates dopant diffusion when an N-type barrier layer is formed below the well layer and a P-type barrier layer is formed above the well layer, but is not limited thereto. The N-type barrier layer-well layer-N-type barrier is not limited thereto. In the layer portion or the P-type barrier layer-well layer-P-type barrier layer portion, the dopant may diffuse into the well layer to reduce the doping effect. Since the dopant diffusion phenomenon reduces the light emitting performance of the optical device, the structure of the semiconductor optical device shown in FIG. 9 is proposed.

9 is a cross-sectional view illustrating a semiconductor device 200 according to another exemplary embodiment of the present invention.

Referring to FIG. 9, a semiconductor device 200 according to another embodiment of the present invention may include an N-type nitride semiconductor layer 20 and a barrier layer, which is a compound semiconductor GaN layer (about 2 micrometers) doped with an N-type dopant. 7.5 nanometer level and the well layer of 2.5-nm or so) the number of times (five times), repeat the MQW (multi quantum well) active layer one _{(30), Al 0 .12 Ga} 0 .88 N layer (20, formed of a structure A structure in which an electron blocking layer (EBL) 40 of about nanometers) and a P-type nitride semiconductor layer 50 of a compound semiconductor GaN layer (about 100 nanometers) doped with a P-type dopant are sequentially stacked Has

In FIG. 9, the N-type nitride semiconductor layer 20, the electron blocking layer (EBL) 40, the P-type nitride semiconductor layer 50, the transparent conductive film 52, and the metal electrodes 52 and 22 are shown in FIG. It can be formed similarly to 1. However, here, the active layer 30 is formed by a method different from that of FIG. 1.

For example, in the semiconductor device 200 according to another embodiment of the present invention, the active layer 30 is a diffusion blocking layer (DBL), a barrier layer, and again a diffusion barrier layer on the N-type nitride semiconductor layer 20. After sequentially forming DBL), the structure may be formed by repeating the formation of the well layer, the formation of the diffusion barrier layer (DBL), the formation of the barrier layer, and the formation of the diffusion barrier layer (DBL). That is, the diffusion barrier layer DBL may be formed before and after forming the barrier layer. The diffusion barrier layer (DBL) may be an undoped GaN film formed in a mixed gas atmosphere including TMGa ((CH3) ₃ Ga) and NH ₃ in a MOCVD apparatus, and in addition, Al _x In _y Ga _{1 -x-} formed in another mixed gas atmosphere. _{It may be a y} N (0 <x <1, 0 <y <1) nitride semiconductor layer. If the barrier layer and the well layer _{Al x In y Ga 1 -x- y} N (0 <x <1, 0 <y <1) of the nitride semiconductor _{layer, Al x In y Ga 1 -x-} y N (0 The diffusion barrier layer (DBL) formed of a <x <1, 0 <y <1) nitride semiconductor layer has Al _x In _y having a lower dopant concentration (N-type or P-type dopant) than the barrier layer or the well layer or having a different composition ratio. _{Ga 1 -x- y N (0 <} x <1, 0 <y <1) may be a nitride semiconductor layer.

Here too, similar to FIG. 1, the barrier layer (s) below the intermediate well layer may be doped with an N type dopant, and the barrier layer (s) above the intermediate well layer may be doped with a P type dopant. For example, as shown in FIG. 10, after the diffusion barrier layer DBL, the barrier layer, and the diffusion barrier layer DBL are sequentially formed on the N-type nitride semiconductor layer 20, a well layer and a diffusion barrier layer DBL are formed thereon. ), The barrier layer, and the diffusion barrier layer (DBL) in the structure is repeated five times in sequence, the lower barrier layer (s) doped with an N-type dopant, based on the third intermediate well layer The barrier layer (s) on top of the third well layer may be doped with a P-type dopant. The N-type dopant may be Si, Ge, Sn, and the like, and the P-type dopant may be Mg, Zn, Cd, Be, Ca, and Ba, and the like. Each dopant may be doped into each layer at a predetermined amount of dopant, for example, a dopant concentration of about 1 * 10 ¹⁹ .

As described above, any kind of the well layer (s) and barrier layer (s) constituting the active layer 30 may be selectively doped with a predetermined dopant (N-type or P-type dopant). For example, only the lower barrier layer of the well layer may be doped with an N type dopant, and only the upper barrier layer of the well layer may be doped with a P type dopant.

In the structure of the semiconductor device as shown in FIG. 10, the diffusion of the dopant from the N-type barrier layer (N-type Al _x Ga _1-x N layer) to the well layer or the P-type is performed by the diffusion barrier layer DBL formed above and below the barrier layer. Diffusion of the dopant from the barrier layer (P-type Al _x Ga _1-x N layer) to the well layer is greatly reduced and can significantly increase the emission intensity in the wavelength range of the visible light region.

The thickness of such a diffusion barrier layer DBL needs to be appropriately selected. As shown in FIG. 11, the thickness of the diffusion barrier layer (DBL) was changed to 5 Å, 10 Å, and 15 시키며. Accordingly, it can be seen that the crystallinity is the best when forming the diffusion barrier layer (DBL) of about 10 에서 in the structure shown in FIG.

The thickness of the diffusion barrier layer (DBL) may be a component or diffusion barrier of an N-type barrier layer (N-type Al _x Ga _{1 - x} N layer), a well layer, and a P-type barrier layer (P-type Al _x Ga _1-x N layer). The thickness of the diffusion barrier layer DBL need not be fixed to 10 kPa as described above, depending on the component of the DBL, the dopant concentration of the barrier layer, or the process conditions for forming the diffusion barrier layer DBL. Note that it can be formed in different thickness according to.

As described above, the present invention has been described by way of limited embodiments and drawings, but the present invention is not limited to the above embodiments, and those skilled in the art to which the present invention pertains various modifications and variations from such descriptions. This is possible. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below but also by the equivalents of the claims.

100: semiconductor device
20: N-type nitride semiconductor layer
30: active layer
40: electron blocking layer
50: P-type nitride semiconductor layer

Claims (9)

A semiconductor device manufacturing method for forming an optical device structure having an active layer and an electron blocking layer (EBL) between an N-type compound semiconductor layer and a P-type compound semiconductor layer,
The active layer includes a multi quantum well (MQW) layer structure,
Forming the MQW layer is,
A first process of forming a barrier layer,
Forming a well layer on the barrier layer, and
A third process of forming a barrier layer on the well layer,
The barrier layer below the well layer or the barrier layer above the well layer is doped with a predetermined dopant. A semiconductor device manufactured by the manufacturing method of claim 1. The method of claim 2,
Forming a diffusion barrier layer (DBL) below the barrier layer before forming the barrier layer below the well layer or the barrier layer above the well layer;
And forming a diffusion barrier layer (DBL) above the barrier layer after forming the barrier layer below the well layer or the barrier layer above the well layer. According to claim 3, wherein the diffusion barrier layer (DBL) is the barrier layer or the dopant concentration than the well layer is low or another composition ratio is _{Al x In y Ga 1 -x- y} N (0 <x <1, 0 <y <1) A semiconductor device comprising a nitride semiconductor layer. The method of claim 2,
And a structure in which the formation of the well layer and the formation of the barrier layer are sequentially repeated a plurality of times over the barrier layer formed by the first process. The method of claim 3,
The well layer is formed on the diffusion barrier layer DBL formed by the fourth process, the barrier layer formed by the first process, and the diffusion barrier layer DBL formed by the fifth process, and the diffusion barrier layer DBL is formed. And a structure in which the formation of the barrier layer and the formation of the diffusion barrier layer (DBL) are sequentially repeated a plurality of times. The method according to claim 5 or 6,
And wherein the barrier layer under the intermediate well layer is doped with an N type dopant, and the barrier layer over the intermediate well layer is doped with a P type dopant in the repeated structure. The semiconductor device according to claim 7, wherein the N-type dopant is any one of Si, Ge, or Sn, and the P-type dopant is any one of Mg, Zn, Cd, Be, Ca, or Ba. The method according to claim 1 or 3,
A semiconductor device, characterized in that the barrier layer and the well layer is _{Al x In y Ga 1 -x- y} N (0 <x <1, 0 <y <1) of the nitride semiconductor layer.

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