KR20010001123A - Fabrication of GaN Semiconductor Light Emitting Device - Google Patents

Abstract

PURPOSE: A method for fabricating a GaN semiconductor light emitting device is provided to increase light emitting efficiency caused by recombination of electrons in an N-type crystallization growth layer and holes in a P-type crystallization growth layer, by preventing a nitrogen out-diffusion and a hydrogen penetration. CONSTITUTION: An N-type contact layer, an N-type clad layer, an active layer, a P-type clad layer and a P-type contact layer are sequentially stacked on a substrate. After the P-type contact layer is formed, the stacked structure is cooled down in an inert gas atmosphere to prevent a nitrogen out-diffusion in a crystallization growth layer and an increase of a hydrogen ion density. The inert gas includes N2, Ar, He or Ne.

Description

Manufacturing method of nitride semiconductor light emitting device {Fabrication of GaN Semiconductor Light Emitting Device}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride semiconductor light emitting device, and more particularly, to a nitride semiconductor light emitting device capable of maximizing hole concentration to increase luminous efficiency by recombination of electron holes.

Nitride semiconductor light emitting devices have recently attracted much attention as materials such as blue light emitting diodes (hereinafter referred to as LEDs), blue laser diodes (hereinafter referred to as LDs), or solar cells.

Among them, the short wavelength blue LEDs in the 400 nm range for the AlGaAs LEDs and LDs in the 800 to 830 nm region enable the information recording density to be increased by four times or more, thus foretelling the arrival of the digital video disc (DVD) era.

In particular, the development of a blue LED achieves the three primary colors of light together with red and green to facilitate the implementation of all natural colors.

1 is a cross-sectional view showing a general nitride semiconductor light emitting device.

In general, a nitride semiconductor light emitting device includes a substrate 100, a buffer layer 110 and an n-type contact layer 120 sequentially formed on the substrate 100, and the n-type contact layer. An n-type clad layer 130 formed on a predetermined portion on the 120, an active layer 140, a p-type clad layer 150, and a p-type contact sequentially formed on the n-type clad layer 130. N-type and p-type electrodes formed on a predetermined portion on the n-type contact layer 120 where the layer 160 and the n-type cladding layer 130 are not formed, and on the p-type contact layer 160, respectively. 170) and 180.

Although not shown in the drawings, wire-bonded to each electrode to make a heat-dissipating heat-sink contact to fabricate a nitride semiconductor light emitting device chip driven by flowing a current through the electrode portion.

In the above, sapphire, GaN, SiC, ZnO, GaAs, or Si is used as the substrate, and GaN, AlN, AlGaN, or InGaN is used as the buffer layer. Chemical Vapor Deposition: Hereinafter, a buffer layer is formed using GaN deposited by MOCVD.

The n-type and p-type contact layers are GaN by n-type and p-type doping, respectively, and the n-type and p-type cladding layers are AlGaN by n-type and p-type doping, respectively. Forms Ti / Al using Ni / Au as the p-type electrode. The p-type layer is mainly formed by doping Mg.

2 is a crystal growth schematic diagram illustrating a method of manufacturing a nitride semiconductor light emitting device according to the related art according to time and temperature.

As shown in FIG. 2, after the substrate is annealed (A) at a high temperature of 1100 ° C., a GaN buffer layer B is formed at a low temperature of 500 ° C. on the annealed substrate. After forming the buffer layer (B), the internal temperature of the chamber is raised to 1100 ° C. to form an n-type contact layer and an n-type clad layer (C), followed by forming an InGaN active layer (D) at 800 ° C. Then, the temperature is raised to 1100 ° C. to form the p-type cladding layer and the p-type contact layer (E), and then the nitride semiconductor light emitting device is cooled by cooling (F) in ammonia (NH ₃ ) gas atmosphere. Form.

3 is a graph showing hydrogen concentration in the depth direction on the p-type GaN surface after p-type GaN crystal growth.

As shown in the graph of FIG. 3, most of the hydrogen components are concentrated and distributed around the p-type GaN surface. This is injected into the ammonia gas atmosphere gas to prevent the formation of N-vacancy due to nitrogen out-diffusion to the GaN surface during the p-type GaN crystal growth process and during temperature cooling after crystal growth. The ammonia gas is thermally decomposed by the temperature inside the chamber at high temperature, and is believed to be due to the penetration into the inside of the GaN surface.

There are some problems with the conventional nitride semiconductor light emitting device having the structure as described above.

First, since the nitride semiconductor light emitting device grows a pn-bonded nitride semiconductor thin film on a sapphire substrate having a different lattice structure, a lattice mismatch exists between the substrate and the upper crystal growth layer. Having a dislocation makes it difficult to obtain a good crystal growth layer.

Second, due to the lattice defects of the crystal-grown thin film, it naturally shows n-type characteristics, and Mg doped to form a p-type contact layer is electrically insulated by combining with H of ammonia (NH ₃ ) gas, which is an atmospheric gas. To form an Mg-H conjugate. Therefore, it is difficult to obtain a high concentration of p-type GaN.

Third, in forming n-type and p-type electrodes for introducing current into the GaN light emitting device, most of the driving voltage is consumed to pass through because of the band gap offset between the GaN surface and the electrode. Therefore, there is a problem that the driving voltage of the device is very large.

Among the above-mentioned problems, the first and third problems have been studied in various ways. Among them, the third problem, the study to minimize the voltage consumed for passing the interface between the GaN surface and the metal electrode, reduces the driving voltage of the light emitting device. The company is actively working to lower the price, but has not reached the commercialization stage yet.

The problem to be solved in the present invention relates to the second problem of the above-described conventional nitride semiconductor light emitting device, wherein the hydrogen content increased by the thermal decomposition of ammonia gas in the p-type crystal growth layer as described above is doped with Mg. By combining to form a high-resistance assembly such as Mg-H, the resistance is more than a few kHz, which causes the driving voltage of the device to increase the lowering of the luminous efficiency of the device.

In other words, a general nitride semiconductor light emitting device is naturally formed by surface nitrogen depletion formed by high temperature crystal growth without any doping to form p-type and n-type GaN layers on an insulating sapphire substrate. n-type conductivity. In this connection, it is difficult to form a p-type GaN layer having a high carrier concentration.

Furthermore, as shown in FIGS. 2 and 3, Mg for p-type doping during the p-type GaN crystal growth by Mg doping and during the cooling process after crystal growth combines with H of ammonia (NH ₃ ), an atmospheric gas, to electrically It is very difficult to obtain a p-type GaN having a high concentration of low resistance characteristics because the Mg-H conjugate having an insulating property of or more is formed.

Accordingly, an object of the present invention is to change the atmospheric gas to lower the concentration of hydrogen ions in the p-type crystal growth layer, thereby increasing the recombination efficiency of electrons in the n-type contact layer and the p-type contact layer holes, thereby increasing the luminous efficiency. The present invention provides a method of manufacturing a light emitting device.

A method for manufacturing a nitride semiconductor light emitting device according to the present invention for achieving the above object has a structure in which an n-type contact layer, an n-type cladding layer, an active layer, a p-type cladding layer and a p-type contact layer are sequentially stacked on a substrate In the nitride semiconductor light emitting device, the p-type contact layer is formed, and then cooled in an inert gas atmosphere to prevent an out diffusion and hydrogen ion concentration of nitrogen components in the crystal growth layer.

1 is a cross-sectional view showing a nitride semiconductor light emitting device.

2 is a schematic view of crystal growth with time and temperature for a method of manufacturing a nitride semiconductor light emitting device according to the prior art;

3 is a graph showing the hydrogen distribution on the surface after p-type GaN crystal growth of a nitride semiconductor light emitting device according to the prior art.

4 is a schematic view of crystal growth according to time and temperature in a method of manufacturing a nitride semiconductor light emitting device according to an embodiment of the present invention.

<Brief description of symbols for the main parts of the drawings>

A, A ': substrate annealing B, B': buffer layer growth

C, C ': n-type layer crystal growth D, D': active layer growth

E, E ': p-type crystal growth F, F': cooling

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

4 is a schematic view illustrating crystal growth according to time and temperature of a method of manufacturing a nitride semiconductor light emitting device according to an embodiment of the present invention.

As shown in FIG. 4, after the substrate is annealed (A ′) at a high temperature of 1100 ° C., a GaN buffer layer B ′ is formed at a low temperature of 500 ° C. on the annealed substrate. After forming the buffer layer B ', the internal temperature of the chamber is raised to 1100 ° C to form an n-type contact layer and an n-type cladding layer (C'), followed by forming an InGaN active layer (D ') at 800 ° C. . Next, the temperature was raised to 1100 ° C. to form the p-type cladding layer and the p-type contact layer (E ′), and then the nitrogen (N ₂ ) gas atmosphere gas instead of the ammonia (NH ₃ ) gas, which is a conventional atmospheric atmosphere gas. The nitride semiconductor light emitting device is formed by a process of cooling (F ′) by using a. As the atmosphere gas of the present invention, an inert gas such as argon (Ar), helium (He), or neon (Ne) may be used instead of nitrogen gas, and in the GaN crystal growth layer during cooling by using the inert gas as the atmosphere gas. It prevents out diffusion of the nitrogen component and prevents the increase of the concentration of hydrogen ions in the crystal growth layer by thermal decomposition of existing ammonia gas. Therefore, it is possible to suppress the production of Mg-H, which is a combination of Mg, which is a conventional p-type dopant, and increased hydrogen due to the atmosphere gas.

Therefore, the method of manufacturing the nitride semiconductor light emitting device according to the present invention prevents out diffusion of nitrogen by cooling in an inert gas atmosphere after crystal growth of the p-type contact layer, as well as infiltration of hydrogen components by thermal decomposition of existing ammonia gas. There is an advantage to increase the luminous efficiency by the constant space recombination of the electron and p-type crystal growth layer of the n-type crystal growth layer by preventing the.

Claims (2)

In a nitride semiconductor light emitting device having a structure in which an n-type contact layer, an n-type cladding layer, an active layer, a p-type cladding layer, and a p-type contact layer are sequentially stacked on a substrate, And forming the p-type contact layer and cooling in an inert gas atmosphere to prevent out diffusion and hydrogen ion concentration of nitrogen components in the crystal growth layer. The method of manufacturing a nitride semiconductor light emitting device according to claim 1, wherein N ₂ , Ar, He, Ne, or the like is used as the inert gas.