CN102157640A

CN102157640A - Method for manufacturing gallium nitride (GaN)-based light-emitting diode (LED) chip with p-GaN layer subjected to surface roughening

Info

Publication number: CN102157640A
Application number: CN 201110064300
Authority: CN
Inventors: 李璟; 王国宏; 魏同波; 张杨; 孔庆峰
Original assignee: Institute of Semiconductors of CAS
Current assignee: Institute of Semiconductors of CAS
Priority date: 2011-03-17
Filing date: 2011-03-17
Publication date: 2011-08-17
Anticipated expiration: 2031-03-17
Also published as: CN102157640B

Abstract

The invention provides a method for manufacturing a gallium nitride (GaN)-based light-emitting diode (LED) chip with a p-GaN layer subjected to surface roughnening, comprising the following steps: adopting a metal organic chemical vapor deposition (MOCVD) method to sequentially grow a low-temperature GaN buffer layer, an undoped GaN layer, an N-GaN layer, a multi-quantum well layer and a P-GaN layer on a semiconductor substrate so as to form a GaN epitaxial wafer; placing the GaN epitaxial wafer into an evaporating table, and evaporating CsCl or chloride on the surface of the P-GaN layer; after the evaporation is ended, injecting water vapor into a cavity of the evaporating table and controlling relative humidity so that the CsCl or chloride on the surface of the P-GaN layer absorbs moisture to gradually enlarge so as to form a CsCl or chloride nanometer island; with the CsCl or chloride nanometer island as an etching mask, etching the GaN epitaxial wafer to form the GaN epitaxial wafer with a roughened surface; etching one side of the GaN epitaxial wafer so as to form a table surface; evaporating a layer of indium tin oxide (ITO) thin film on the upper surface of the GaN epitaxial wafer; and finally manufacturing a P electrode on the upper surface of the GaN epitaxial wafer and manufacturing an N electrode on the table surface.

Description

Manufacture method with GaN base LED chip of p-GaN laminar surface alligatoring

Technical field

The present invention relates to the photoelectric device field, be specifically related to the manufacture method of the GaN base LED chip of a kind of p-GaN of having laminar surface alligatoring.

Background technology

Light-emitting diode (Light Emitting Diode is called for short LED) is the electroluminescence solid state light emitter that a kind of low-voltage direct drives, and it has the colorimetric purity height, and response speed is fast, and volume is little, good reliability, and the life-span is long, advantages such as environmental protection.These advantages of led light source, with causing the revolution of Lighting Industry technology and application, substitute electron tube as semiconductor transistor, after the several years, with the solid-state illumination lamp of LED, replace traditional illuminating lamp gradually with having an opportunity and enter common people house as new light sources.

At present, generally adopt the epitaxial wafer of Sapphire Substrate to prepare high efficiency GaN base LED.The luminous efficiency that how to improve GaN base LED is a research emphasis all the time.Development along with growth technology and multi-quantum pit structure, the internal quantum efficiency of super brightness Light-Emitting Diode has had very large raising, the LED internal quantum efficiency of blue light GaN base can reach more than 70% at present, but the external quantum efficiency of high-power LED chip has only about 40% usually, the low raising that has influenced external quantum efficiency of the light extraction efficiency of high-power LED chip has influenced the raising of final light extraction efficiency.This is because the refractive index (n=2.5) of GaN material differs bigger with air (n=1) and Sapphire Substrate (n=1.75), cause the critical angle that total reflection takes place for air and GaN interface and sapphire and GaN interface to have only 23.6 ° and 44.4 ° respectively, the light that active area produces has only minority to escape into outside the material bodies.This just requires to design from the chip structure aspect, reduces total reflection, increases the critical angle of escape light cone, improves the light extraction efficiency of high-power chip.The main technical schemes that adopts both at home and abroad has at present: growth distribution bragg reflection layer (DBR) structure, surface coarsening technology and photonic crystal technology etc.Surface coarsening fabrication techniques technology is simple than DBR and photonic crystal, cost is low, is the technology of generally being had an optimistic view of at present.Surface coarsening is divided into two kinds of wet method alligatoring and dry method alligatoring.The wet method alligatoring is to utilize strong acid or alkali corrosion GaN material surface, forms the coarse effect of nature, as patent CN101248537 and CN101409321.But there are shortcomings such as isotropism, easy undercutting and mistake erosion in the wet method alligatoring, and the size and the degree of depth of alligatoring are restricted, and be not obvious for effective extraction effect of light.The dry method alligatoring is to shelter by mask, adopts ICP etching GaN material surface to reach the effect of roughening.The dry method alligatoring has advantages such as anisotropic etching, etch rate be fast.Mask how to make nanometer scale is the difficult point of dry method roughening process.Patent CN101702419 adopts spin-coating method to apply the mask of Ni nano particle as dry etching, patent CN101656284 adopts the mask of ITO particle as dry etching, these methods all exist can't accurately control mask size and inhomogeneity shortcoming, cause the effect of 2 inches GaN sheet surface coarsenings inconsistent, the raising of light extraction efficiency is inhomogeneous.And the removal of mask need use the strong acid class, and strong acid can make the oxidation of GaN material surface, causes the device forward voltage to raise.

Summary of the invention

At defective and the deficiency that existing dry method alligatoring P-GaN material mask exists, the invention provides the manufacture method of the GaN base LED chip of a kind of p-GaN of having laminar surface alligatoring, it is simple that this method has technology, and cost is low, and alligatoring is effective, the light extraction efficiency height.Improve more than 70% through the GaN-LED behind the surface coarsening than the luminous power of conventional GaN-LED.

The invention provides the manufacture method of the GaN base LED chip of a kind of p-GaN of having laminar surface alligatoring, comprise the steps:

Step 1: adopt the method for metal organic chemical vapor deposition, growing low temperature GaN resilient coating, the GaN layer that undopes, N-GaN layer, multiple quantum well layer and P-GaN layer successively on Semiconductor substrate form the GaN epitaxial wafer;

Step 2: the GaN epitaxial wafer is put into evaporator, at the surperficial evaporation CsCl or the chloride of P-GaN layer;

Step 3: after evaporation finishes, charge into steam in the evaporator chamber, control relative humidity makes the CsCl of P-GaN laminar surface or chloride absorb moisture to grow up gradually and form CsCl or muriatic nanometer island;

Step 4: etching as etch mask, is carried out to the GaN epitaxial wafer in CsCl or chloride nanometer island, form the GaN epitaxial wafer of surface coarsening;

Step 5 a: again side of GaN epitaxial wafer is carried out etching, form table top;

Step 6: at upper surface evaporation one deck ito thin film of GaN epitaxial wafer;

Step 7: the upper surface at the GaN epitaxial wafer is made the P electrode, makes the N electrode on table top, finishes the device preparation.

Wherein said Semiconductor substrate 1 is sapphire, silicon, carborundum or metal.

Wherein the diameter on nanometer island is the 100-20000 nanometer.

Use Cl when wherein the GaN epitaxial wafer being carried out etching ₂/ BCl ₃/ Ar ₂As etching gas, BCl ₃Flow is 3-20sccm, Ar ₂Flow is 3-25sccm, Cl ₂Flow is 30-100sccm; Etching power is 300-700W; Radio-frequency power is 50-200W; Etch period is 10s-10min.

Wherein the roughness of the GaN epitaxial wafer of surface coarsening is 5nm-50nm.

Wherein the etching depth of table top arrives in the N-GaN layer.

When wherein the P-GaN layer being carried out surface coarsening, the degree of depth of institute's etching is less than 1/2 of thickness.

Description of drawings

For further specifying technology contents of the present invention, the invention will be further described below in conjunction with accompanying drawing, wherein:

Fig. 1 is the structural representation of conventional GaN base LED.

Fig. 2 is that the present invention passes through the structural representation that the alligatoring of P-GaN laminar surface improves the GaN base LED of light extraction efficiency.

Fig. 3 is the GaN base LED current-voltage correlation correlation curve figure of the present invention and prior art.

Fig. 4 is that the GaN base LED current power of the present invention and prior art concerns correlation curve figure.

Embodiment

See also shown in Figure 1ly, the invention provides the manufacture method of the GaN base LED chip of a kind of p-GaN of having laminar surface alligatoring, comprise the steps:

Step 1: the method that adopts metal organic chemical vapor deposition (MOCVD), 1 μ m low temperature GaN resilient coating, 2, the 1 μ m that on Semiconductor substrate 1, grows successively undope

GaN layer

3,3 μ mN-GaN layer 4,150nm multiple quantum well light emitting layer 5 and 300nmP-GaN layer 6, form the GaN epitaxial wafer, wherein said Semiconductor substrate 1 is sapphire, silicon, carborundum or metal;

Step 2: the GaN epitaxial wafer is put into evaporator, and at surperficial evaporation etching the mask CsCl or the chloride of P-GaN layer 6, this chloride is LiCl, KCl, NaCl, AgCl, TiCl etc.;

Step 3: after evaporation finishes, in the evaporator chamber, charge into steam, control relative humidity makes the CsCl on P-GaN layer 6 surface or chloride absorb moisture to grow up gradually and form CsCl or muriatic nanometer island, and the diameter on this nanometer island is the 100-20000 nanometer, duty ratio 1: 1;

Step 4: ICP (inductively coupled plasma) etching as etch mask, is carried out to the GaN epitaxial wafer in CsCl or chloride nanometer island, use Cl ₂, BCl ₃, Ar ₂As etching gas, Cl wherein ₂Flow is 30-100sccm, BCl ₃Flow is 3-20sccm, Ar ₂Flow is 3-25sccm; Etching power is 300-700W; Radio-frequency power is 50-200W; Etch period is 10s-10min.Remove CsCl on the GaN epitaxial wafer or chloride mask clean with deionized water after etching finishes, the P-GaN surface roughness is 5nm-50nm, forms the GaN epitaxial wafer of surface coarsening thus, and purpose is in order to increase the emergent light area, increase the exit probability of light, reduce the generation of total reflection.When the P-GaN layer was carried out surface coarsening, the degree of depth of institute's etching was less than 1/2 of thickness;

Step 5: again the GaN epitaxial wafer is carried out the litho pattern preparation, select for use the AZ4620 photoresist as mask, a side of GaN epitaxial wafer is carried out the ICP etching, remove P-GaN, quantum well and the part N-GaN of a side, form table top 41, the etching depth 700nm-1500nm of this table top 41;

Step 6: make the method evaporation ito thin film 7 of deposited by electron beam evaporation, thickness 2400 at the upper surface of GaN epitaxial wafer

Select AZ6130 photoresist and little chloroazotic acid (3HCl: HNO for use ₃) photoetching corrosion goes out the ITO figure, removes part ito thin film on the P-GaN 6 and the ito thin film on the table top 41, forms ito transparent electrode on P type table top.Ito transparent electrode and P-GaN can form good Ohmic contact, can reduce touch voltage, thereby reduce the operating voltage of device;

Step 7: on P-GaN layer 6, ITO layer 7 and N-GaN layer 41, select negative photoresist L-300 photoetching P, N electrode for use, adopt electron-beam vapor deposition method evaporation metal CrPtAu (100/500/10000 ), peel off the back and form P electrode 8 and N electrode 9.The thickness of P, N electrode metal is thicker, routing test when being convenient to packaged chip;

Step 8: the reducing thin of sapphire substrate of slice, thin piece to 150um, is drawn and is cleaved into independent chip, carry out the I-V characteristic test and the P-I characteristic test of device.

Above-described specific embodiment, purpose of the present invention, technical scheme and beneficial effect are further described, institute is understood that, the above only is specific embodiments of the invention, be not limited to the present invention, within the spirit and principles in the present invention all, any modification of being made, be equal to replacement, improvement etc., all should be included within the claim scope of the present invention.

Claims

1. the manufacture method with GaN base LED chip of p-GaN laminar surface alligatoring comprises the steps:

2. the manufacture method with GaN base LED chip of p-GaN laminar surface alligatoring according to claim 1, wherein said Semiconductor substrate 1 is sapphire, silicon, carborundum or metal.

3. the manufacture method with GaN base LED chip of p-GaN laminar surface alligatoring according to claim 1, wherein the diameter on nanometer island is the 100-20000 nanometer.

4. the manufacture method with GaN base LED chip of p-GaN laminar surface alligatoring according to claim 1 is used Cl when wherein the GaN epitaxial wafer being carried out etching ₂/ BCl ₃/ Ar ₂As etching gas, BCl ₃Flow is 3-20sccm, Ar ₂Flow is 3-25sccm, Cl ₂Flow is 30-100sccm; Etching power is 300-700W; Radio-frequency power is 50-200W; Etch period is 10s-10min.

5. the manufacture method with GaN base LED chip of p-GaN laminar surface alligatoring according to claim 1, wherein the roughness of the GaN epitaxial wafer of surface coarsening is 5nm-50nm.

6. the manufacture method with GaN base LED chip of p-GaN laminar surface alligatoring according to claim 1, wherein the etching depth of table top arrives in the N-GaN layer.

7. the manufacture method with GaN base LED chip of p-GaN laminar surface alligatoring according to claim 5, when wherein the P-GaN layer being carried out surface coarsening, the degree of depth of institute's etching is less than 1/2 of thickness.