KR100730752B1 - Compound semiconductor having supper lattice layer and light emitting diode using the same and method for fabricating the ligth emitting diode - Google Patents

Abstract

A compound semiconductor having a super lattice layer, a light emitting diode using the same, and a manufacturing method thereof are provided to implement a high quality GaN-based conductive semiconductor layer by sequentially forming the super lattice layer and an undoped GaN semiconductor layer on a buffer layer. A buffer layer(210) is disposed on a substrate(100). A super lattice layer(220) is disposed on the cuffer layer. A GaN layer and a GaNP layer are stacked in turn on the super lattice layer as pre-set numbers. A first conductive semiconductor layer(310) is located on the super lattice layer. An active layer(320) is located on a partial region of the first conductive semiconductor layer. A second conductive semiconductor layer(330) is located on the active layer. An undoped GaN semiconductor layer(230) is disposed between the super lattice layer and the first conductive semiconductor layer.

Description

Compound semiconductor having a superlattice layer, a light emitting diode using the same, and a method of manufacturing the same {compound semiconductor having supper lattice layer and light emitting diode using the same and method for fabricating the ligth emitting diode}

1 is a cross-sectional view of a light emitting diode according to an embodiment of the present invention.

2 is a flowchart of a method of manufacturing a light emitting diode 1 according to an embodiment of the present invention.

3A to 3C are cross-sectional views illustrating a method of manufacturing a light emitting diode according to an embodiment of the present invention.

4 is a flowchart of a method of manufacturing a light emitting diode 2 according to another embodiment of the present invention.

5A to 5C are cross-sectional views illustrating a method of manufacturing a light emitting diode 2 according to another embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

1,2: light emitting diode 100: substrate

210: low temperature buffer layer 220: superlattice layer

230: undoped GaN semiconductor layer 310: first conductive semiconductor layer

320: active layer 330: second conductive semiconductor layer

400: transparent electrode 500a, 500b, 700a, 700b: electrode pad

600: reflective layer

The present invention relates to a compound semiconductor having a superlattice layer, a light emitting diode using the same, and a method of manufacturing the same. In particular, a compound semiconductor capable of forming a high quality conductive semiconductor layer by sequentially forming a superlattice layer on a buffer layer, It relates to a light emitting diode used and a method of manufacturing the same.

A light emitting diode is a photoelectric conversion semiconductor device having a structure in which an N-type semiconductor and a P-type semiconductor are bonded to each other, and emit light by recombination of electrons and holes. Such light emitting diodes are widely used as display devices and backlights. In addition, the light emitting diode consumes less power and has a longer life compared to a conventional light bulb or a fluorescent lamp, thereby replacing the incandescent bulb and the fluorescent lamp, thereby expanding its use area as a general lighting application.

A light emitting diode is used as a substrate forming the base sapphire substrate lot of good reliability are those above the _{Al x In y Ga 1 -x- y} N (0≤x, y, x + y≤1) semiconductor layer, that is, the GaN-based semiconductor The layer is grown. In particular, in the case of green and blue light emitting diodes, there are many light emitting diodes using GaN-based semiconductor layers having a high band gap.

However, due to the lattice mismatch between the GaN-based semiconductor layer and the substrate, the GaN-based semiconductor layer grown on the substrate has a problem of high defect density, which causes problems such as deterioration of reliability, productivity, and electrical properties of the light emitting diode.

In order to solve this problem, a conventional light emitting diode is manufactured by employing a method of growing a GaN buffer layer on a substrate and growing a doped GaN conductive semiconductor layer thereon.

However, in the conventional light emitting diode, the GaN buffer layer has a high defect density due to the difference in lattice constant between the substrate and the GaN buffer layer grown on the substrate, and the doped GaN conductive semiconductor layer grown thereon is also high due to high stress. There is a problem with a defect density.

In particular, in the case of a vertical LED (VLED), after the growth of the buffer layer on the substrate and forming a GaN-based conductive semiconductor layer thereon, the substrate and the buffer layer is etched and removed. In this case, when the defect density of the GaN-based conductive semiconductor layer is high, the active layer on the GaN-based conductive semiconductor layer is exposed during the etching process.

To solve this problem, there is a method of thickening the buffer layer, but there is a problem in that additional manufacturing time and material are required.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems, and to provide a high-quality GaN-based semiconductor layer having a low defect density on top of a substrate having a different lattice constant without increasing manufacturing time and material requirements.

According to an aspect of the present invention for achieving the above object, a buffer layer; A superlattice layer disposed on the buffer layer, in which GaN films and GaNP films are alternately stacked by a predetermined number; And a (Al, In, Ga) N semiconductor layer located on the superlattice layer.

According to another aspect of the present invention for achieving the above object, a substrate; A buffer layer on the substrate; A superlattice layer disposed on the buffer layer, in which GaN films and GaNP films are alternately stacked by a predetermined number; A first conductive semiconductor layer on the superlattice layer; An active layer on a portion of the first conductive semiconductor layer; And a second conductive semiconductor layer on the active layer.

Preferably, the semiconductor layer further comprises an undoped GaN semiconductor layer interposed between the superlattice layer and the first conductive semiconductor layer.

More preferably, the superlattice layer is formed by stacking 5 to 50 pairs of the GaN film and the GaNP film.

According to another aspect of the present invention for achieving the above object, a superlattice layer is prepared by preparing a substrate, forming a buffer layer on the substrate, and alternately stacking a GaN film and a GaNP film on the buffer layer by a predetermined number. And forming a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer on the superlattice layer.

Preferably, the method further includes forming an undoped GaN semiconductor layer on the superlattice layer before forming the first conductive semiconductor layer.

More preferably, the superlattice layer is formed by stacking 5 to 50 pairs of the GaN film and the GaNP film.

More preferably, a transparent electrode is formed on the second conductive semiconductor layer,

The substrate and the superlattice layer are removed to expose one surface of the first conductive semiconductor layer, a reflective layer is formed on an exposed surface of the first conductive semiconductor layer, and a portion of the transparent electrode and the reflective layer is formed. It further comprises forming an electrode pad.

More preferably, a transparent electrode is formed on the second conductive semiconductor layer, the substrate, the superlattice layer, and the undoped GaN semiconductor layer are removed to expose one surface of the first conductive semiconductor layer. The method may further include forming a reflective layer on an exposed surface of the conductive semiconductor layer and forming an electrode pad on a portion of the transparent electrode and the reflective layer.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view of a light emitting diode according to an embodiment of the present invention.

Referring to FIG. 1, a light emitting diode 1 according to an embodiment of the present invention may include a substrate 100, a buffer layer 210, a superlattice layer 220, and an undoped GaN semiconductor layer 230. And a first conductive semiconductor layer 310, an active layer 320, a second conductive semiconductor layer 330, a transparent electrode 400, and first and second electrode pads 500a and 500b.

The substrate 100 may be made of a material such as sapphire, spinel, Si, SiC, or the like.

The buffer layer 210 is used to mitigate the lattice mismatch between the semiconductor layers to be formed thereon and the substrate 100. The buffer layer 210 may be, for example, an AlN or GaN layer and may be grown at a low temperature, for example, about 400 to about 700 degrees Celsius.

The buffer layer 210 is a low-quality GaN-based semiconductor layer, and there are many defects such as dislocations due to a difference in lattice constant from the substrate 100. That is, when the first conductive semiconductor layer 310, which is the GaN based semiconductor layer, is directly formed on the buffer layer 210, the buffer layer 210 has a high defect density. It has a defect density, thereby deteriorating the electrical characteristics such as the luminous efficiency of the light emitting diode (1). This will fall.

The thickness of the buffer layer may be, for example, about 20 nm to about 50 nm.

To solve this problem, the superlattice layer 220 and the undoped GaN semiconductor layer 230 are sequentially formed on the buffer layer 210.

The superlattice layer 220 is disposed on the buffer layer 210, and a GaN film and a GaNP film are alternately stacked by a predetermined number, for example, 5 to 50 pairs.

The superlattice layer 220 is a semiconductor layer provided to grow the undoped GaN semiconductor layer 230 of high quality with low defect density and good crystallinity. That is, the P atoms of the GaNP film move to the existing defects to eliminate the defects, thereby forming the thin undoped GaN semiconductor layer 230 with high quality on the superlattice layer 220. Can be.

The thickness of each GaN film and GaNP film included in the superlattice layer 220 may be about 5.5 nm or less, for example, and the thickness of the superlattice layer 220 may be about 50 nm or less.

The undoped GaN semiconductor layer 230 is interposed between the superlattice layer and the first conductive semiconductor layer 310 and is made of undoped GaN.

The undoped GaN semiconductor layer 230 provides a high quality GaN semiconductor layer so as to effectively form the first conductive semiconductor layer 310 made of GaN-based material thereon with high quality.

The undoped GaN semiconductor layer 230 may have a thickness of about 1 μm or less, for example. When the superlattice layer 220 is not interposed between the buffer layer 210 and the undoped GaN semiconductor layer 230, the undoped GaN semiconductor of the same quality as compared with the case where the superlattice layer 220 is interposed. In order to obtain the layer 230, the thickness of the undoped GaN semiconductor layer 230 should be, for example, about 2 μm thick.

Since the superlattice layer 220 is interposed between the buffer layer 210 and the undoped GaN semiconductor layer 230, the high quality undoped GaN semiconductor layer 230 can be grown faster using less material. have.

The first conductive semiconductor layer 310 may be formed of N-type _{Al x In y Ga 1 -x- y} N (0≤x, y, x + y≤1), may include the N-type clad layer have. The first conductive semiconductor layer 310 may be formed by doping silicon (Si).

The active layer 320 is an area where electrons and holes are recombined and includes InGaN. The emission wavelength emitted from the light emitting diode 1 is determined according to the type of material constituting the active layer 320. The active layer 320 may be a multilayer film in which a quantum well layer and a barrier layer are repeatedly formed. The barrier layer and the well layer may be binary to quadruple compound semiconductor layers represented by general formula Al _x In _y Ga _1-xy N (0 ≦ x, y, x + y ≦ 1).

The second conductive semiconductor layer 330 may be formed of P-type _{Al x In y Ga 1 -x- y} N (0≤x, y, x + y≤1), may include a P-type clad layer have. The second conductive semiconductor layer 330 may be formed by doping zinc (Zn) or magnesium (Mg).

The light emitting diode 1 has a structure in which the first conductive semiconductor layer 310, the active layer 320, and the second conductive semiconductor layer 330 are sequentially stacked. The active layer 320 is formed on a portion of the first conductive semiconductor layer 310, and the second conductive semiconductor layer 330 is formed on the active layer 320. Therefore, a portion of the upper surface of the first conductive semiconductor layer 310 is bonded to the active layer 320, and a portion of the upper surface of the first conductive semiconductor layer 310 is exposed to the outside.

The transparent electrode 400 is formed on the second conductive semiconductor layer 330. The transparent electrode 400 has a plate shape and transmits light emitted from the active layer 320 to the outside. The transparent electrode 400 may be formed of a transparent material such as Ni / Au or indium tin oxide (ITO). The transparent electrode 400 evenly distributes the current input through the electrode pad 500a to increase the luminous efficiency.

The first and first electrode pads 500a and 500b are formed on the transparent electrode 400 and on the first conductive semiconductor layer 310. The electrode pads 500a and 500b are connected to a lead (not shown) by a wire to receive power from an external power source.

2 is a flowchart illustrating a method of manufacturing the light emitting diode 1 according to an embodiment of the present invention, and FIGS. 3A to 3C are cross-sectional views illustrating a method of manufacturing the light emitting diode 1 according to an embodiment of the present invention. admit.

2 and 3A, the substrate 100 is prepared (S100). The substrate 100 may be a substrate made of a material such as sapphire, spinel, Si, SiC, or the like.

Thereafter, a buffer layer 210 is formed on the substrate 100 (S110). For example, the buffer layer 210 may be grown to a thickness of 20 nm to 50 nm under a temperature of about 400 degrees to about 1300 degrees and a pressure of 50 Torr to 700 Torr.

Thereafter, a GaNP film and a GaN film are alternately stacked on the buffer layer 210 to form a superlattice layer 220 (S120). The superlattice layer 220 may be grown to a thickness of about 50 nm or less, for example, under a temperature of about 400 degrees to about 1300 degrees and a pressure of 50 Torr to 700 Torr.

Thereafter, an undoped GaN semiconductor layer 230 is formed on the superlattice layer 220 (S130). The superlattice layer 220 may be grown to a thickness of about 1 μm or less, for example, at a temperature of about 800 degrees to about 1300 degrees and a pressure of 50 Torr to 700 Torr.

The buffer layer 210, the superlattice layer 220, and the undoped GaN semiconductor layer 230 may include metal organic chemical vapor deposition (MOCVD) and hydride vapor phase epitaxy (HVPE). Alternatively, it may be formed using a molecular beam epitaxy (MBE) or the like.

Referring to FIGS. 2 and 3B, the first conductive semiconductor layer 310, the active layer 320, and the second conductive semiconductor layer 330 are sequentially formed on the undoped GaN semiconductor layer 230 (S140). ).

The semiconductor layers 310, 320, and 330 may be formed using metal organic chemical vapor deposition (MOCVD), hydride vapor deposition (HVPE), molecular beam growth (MBE), or the like. In addition, the semiconductor layers 310, 320, and 330 may be continuously formed in the same process chamber.

Thereafter, the transparent electrode 400 is formed on the second conductive semiconductor layer 330 (S150).

Referring to FIGS. 2 and 3C, the transparent electrode 400, the second conductive semiconductor layer 330, and the active layer 320 are patterned or etched using a photolithography and etching process to form the first conductive semiconductor. A portion of the upper portion of the layer 310 is exposed (S160).

Thereafter, first and second electrode pads 500a and 500b are formed on upper surfaces of the transparent electrode 400 and the exposed first conductive semiconductor layer 310, respectively (S170). The electrode pads 500a and 500b may be formed using a lift off method.

4 is a flowchart of a method of manufacturing a light emitting diode 2 according to another embodiment of the present invention, and FIGS. 5A to 5C are cross-sectional views illustrating a method of manufacturing a light emitting diode 2 according to another embodiment of the present invention. admit.

Referring to FIGS. 4 and 5A, the substrate 100 is prepared (S200). The substrate 100 is preferably a substrate made of a light transmissive material such as sapphire.

Thereafter, a buffer layer 210 is formed on the substrate 100 (S210).

Subsequently, a superlattice layer 220 is formed by alternately stacking GaNP films and GaN films on the buffer layer 210 by a predetermined number, for example, 5 to 50 pairs (S220).

Thereafter, an undoped GaN semiconductor layer 230 is formed on the superlattice layer 220 (S230).

Methods of forming the buffer layer 210, the superlattice layer 220, and the undoped GaN semiconductor layer 230 are described in detail with reference to FIG. 3A, and the undoped GaN semiconductor layer 230 has a low defect density. Have

Referring to FIGS. 4 and 5B, a first conductive semiconductor layer 310, an active layer 320, and a second conductive semiconductor layer 330 are sequentially formed on the undoped GaN semiconductor layer 230 (S240). ).

Since the first conductive semiconductor layer 310 is formed on the high-quality undoped GaN semiconductor layer 230 having a low defect density, defects such as dislocations and the like have good quality.

Thereafter, the transparent electrode 400 is formed on the second conductive semiconductor layer 330 (S250).

Thereafter, the laser beam is irradiated toward the substrate 100 to separate the substrate 100 from the superlattice layer 220 (S260).

When using a laser, it is preferable that the said board | substrate 100 is a translucent board which transmits a laser beam like a sapphire board | substrate. The substrate 100 is irradiated with a laser, which may be, for example, a KrF (248 nm) laser. Since the substrate 100 is a light transmissive substrate, the low temperature buffer layer 210 interface is decomposed by the absorbed energy at the interface between the substrate 100 and the low temperature buffer layer 210, so that the substrate 100 is decomposed. Are separated.

The substrate 100 may be separated using, for example, polishing, dry etching or wet etching techniques instead of using a laser.

Referring to FIGS. 4 and 5C, after the substrate 100 is separated, the superlattice layer 220 and the undoped GaN semiconductor layer 230 are etched to form the first conductive semiconductor layer 310. Expose one surface of (S270).

The first conductive semiconductor layer 310 has a low defect density and good surface properties for easy etching. When the quality of the first conductive semiconductor layer 310 is low, the active layer 320 may be exposed when the undoped GaN semiconductor layer 230 is etched, but the first conductive semiconductor layer grown according to the present invention ( 310 does not have this problem.

Thereafter, the reflective layer 600 is formed on the exposed surface of the first conductive semiconductor layer 310 (S280).

The reflective layer 600 may be formed of, for example, Ag and / or Al, and reflects light emitted from the active layer 320 upward to increase the luminous efficiency of the light emitting diode 2.

Thereafter, first and second electrode pads 500a and 500b are formed on the transparent electrode 400 and the reflective layer 600 (S290). The electrode pads 500a and 500b may be formed by a lift off method.

The compound semiconductor in which the superlattice layer 220 and the undoped GaN semiconductor layer 230 are sequentially formed on the buffer layer 210 may be prepared by those skilled in the art for manufacturing not only the light emitting diodes 1 and 2 but also other semiconductor devices such as a laser. Of course, it can be used easily.

The present invention is not limited to the embodiments described above, and various modifications and changes can be made by those skilled in the art, which are included in the spirit and scope of the present invention as defined in the appended claims.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems, by sequentially forming a superlattice layer and an undoped GaN semiconductor layer on a buffer layer, so that the defect density is low on top of a substrate having a different lattice constant without increasing manufacturing time and material requirements. There is an effect that a high quality GaN-based conductive semiconductor layer can be formed.

Claims (9)

Buffer layer; A superlattice layer disposed on the buffer layer, in which GaN films and GaNP films are alternately stacked by a predetermined number; A (Al, In, Ga) N semiconductor layer on the superlattice layer; Compound semiconductor comprising a. Board, A buffer layer on the substrate, A superlattice layer disposed on the buffer layer, in which GaN films and GaNP films are alternately stacked by a predetermined number; A first conductive semiconductor layer on the superlattice layer; An active layer on a portion of the first conductive semiconductor layer; And A light emitting diode comprising a second conductive semiconductor layer on the active layer. The method according to claim 2, An undoped GaN semiconductor layer interposed between the superlattice layer and the first conductive semiconductor layer; Light emitting diodes further comprising. The light emitting diode of claim 2, wherein the superlattice layer is formed by stacking 5 to 50 pairs of the GaN film and the GaNP film. Prepare the substrate, Forming a buffer layer on the substrate, Alternately stacking a GaN film and a GaNP film on the buffer layer by a predetermined number to form a superlattice layer, Forming a first conductive semiconductor layer, an active layer, and a second conductive semiconductor layer on the superlattice layer. The method according to claim 5, And forming an undoped GaN semiconductor layer on the superlattice layer prior to forming the first conductive semiconductor layer. The method of claim 5, wherein the superlattice layer comprises 5 to 50 pairs of the GaN film and the GaNP film. The method according to claim 5, Forming a transparent electrode on the second conductive semiconductor layer, Removing the substrate and the superlattice layer to expose one surface of the first conductive semiconductor layer, Forming a reflective layer on the exposed one surface of the first conductive semiconductor layer, And forming an electrode pad on a portion of the transparent electrode and the reflective layer. The method according to claim 6, Forming a transparent electrode on the second conductive semiconductor layer, Removing the substrate, the superlattice layer, and the undoped GaN semiconductor layer to expose one surface of the first conductive semiconductor layer, Forming a reflective layer on the exposed one surface of the first conductive semiconductor layer, And forming an electrode pad on a portion of the transparent electrode and the reflective layer.

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