CN102394261A

CN102394261A - Method of epitaxially growing nitride epitaxial film on sapphire patterned substrate

Info

Publication number: CN102394261A
Application number: CN2011103650101A
Authority: CN
Inventors: 李鸿渐; 李盼盼; 李志聪; 李璟; 王国宏
Original assignee: YANGZHOU ZHONGKE SEMICONDUCTOR LIGHTING CO Ltd
Current assignee: YANGZHOU ZHONGKE SEMICONDUCTOR LIGHTING CO Ltd
Priority date: 2011-11-17
Filing date: 2011-11-17
Publication date: 2012-03-28
Anticipated expiration: 2031-11-17
Also published as: CN102394261B

Abstract

The invention discloses a method of epitaxially growing a high-quality nitride epitaxial film on a sapphire patterned substrate. By utilizing a metal-organic chemical vapor deposition (MOVCD) method and adopting two-step growth technology, and through optimizing growing conditions, GaN is controlled to be subjected to appropriate three-dimensional growth on the sapphire patterned substrate, and then is converted to be subjected to two-dimensional growth, so that the high-quality nitride epitaxial film can be obtained. In the method, the characteristics of the sapphire patterned substrate are fully utilized, and the obtained nitride epitaxial film has the characteristics of low dislocation density, mirror surface, small half width of XRD (X-Ray Diffraction), and the like. By adopting the method to conduct the nitride epitaxy, a growing window is wide, so that the method is applicable to commercialized growth of the high-quality nitride epitaxial film.

Description

The method of epitaxial growth nitride epitaxial film on the sapphire graphical substrate

Technical field

The invention belongs to the optical semiconductor electro-technical field, be meant especially a kind of on the sapphire graphical substrate method of epitaxial growth high-quality nitride epitaxial film.

Background technology

Advantages such as the basic LED of gallium nitride (GaN) is just efficient with it once occurring as solid state light emitter, long-life, environmental protection; Be described as after Edison invents electric light the historical revolution second time of human illumination, become the focus of semiconductor and lighting field research and development and industry concern in the world.But GaN base LED gets into the general illumination field at present, is also to face many difficult problems in technology and cost.

Sapphire Substrate is one of commercial nitride heteroepitaxial growth substrate the most commonly used at present.Adopt the graphic sapphire substrate can increase light, and then improve the light extraction efficiency of LED in the inner total reflection of LED.Than common sapphire plane substrate, the nitride based blue-ray LED power output of epitaxial growth can improve 30% ~ 100% on the sapphire graphical substrate.High-brightness nitride base blue-ray LED epitaxial wafer major part epitaxial growth on the sapphire graphical substrate of present commercial usefulness obtains.Adopt the narrow graph substrate of figure spacing, for example the figure spacing is 1 μ m, and the power output of its acquisition is the highest.But epitaxial growth nitride on this thin space graph substrate, its growth window is little, and is responsive to temperature fluctuation, in commercially producing process, occurs easily because the fluctuation of MOCVD system temperature causes a series of problems such as the epitaxial film surface is crude.Therefore on the sapphire graphical substrate, obtaining to have the surface has difficulties for minute surface, the wide high-quality nitride epitaxial film of growth window.

Summary of the invention

The object of the present invention is to provide a kind of high-quality on the sapphire graphical substrate method of epitaxial growth nitride epitaxial film.

Technical scheme of the present invention may further comprise the steps:

1) on the sapphire graphical substrate, adopt metal-organic chemical vapor deposition equipment (MOCVD) the method low temperature buffer layer of growing, said growth temperature is 400 ℃～600 ℃, thickness is 5nm～100nm;

2) be warmed up to crystallization again under 950 ℃～1100 ℃ conditions, on Sapphire Substrate, form seed crystal;

3) be that 500～1200 ︰ 1, growth temperature are that 900 ℃～1020 ℃, pressure are under the condition of 300～600mbar in the mol ratio of Ga and N, growth 500s～2000s; Can make GaN be in the island growth pattern, carry out sufficient three dimensional growth, not cross the figure top;

4) be that 1000～2000 ︰ 1, growth temperature are that 1020 ℃～1070 ℃, pressure are under the condition of 100～500mbar in the mol ratio of Ga and N, growth 100s～4000s.Can make the GaN growth pattern turn to the two-dimensional growth pattern, make GaN closed, form continuous GaN epitaxial film at the graph substrate top from the island growth pattern.

The present invention is at first through control growing condition (mol ratio of temperature, pressure, Ga and N and growth time), carries out at the beginning with the longitudinal growth being main three dimensional growth and making GaN not have the figure top; Optimize growth conditions then, make three dimensional growth mode switch two-dimensional growth pattern to let GaN, to obtain high-quality nitride epitaxial film in the adequate closure of figure top.The method makes full use of the characteristics of graph substrate, and principle is similar to horizontal extension (ELOG), when control turns to the two-dimensional growth pattern by the three dimensional growth pattern, can reduce dislocation density so that most of dislocation turns to; Through the control closing speed, fully discharge the stress that causes by GaN and sapphire lattice mismatch simultaneously, to improve crystal mass; Through optimizing the three dimensional growth condition, the pattern behind the control three dimensional growth can be widened the GaN growth window.Characteristics such as it is low that the nitride epitaxial film that therefore adopts the method to obtain has dislocation density, and the surface is a minute surface, and the low and growth window of XRD half-breadth is wide are particularly suitable in commercial employing, have very high practical value.

The present invention adopts two one-step growth technologies, and through optimizing growth conditions, control GaN three dimensional growth on the sapphire graphical substrate turns to two-dimensional growth then, to obtain high-quality nitride epitaxial film.Characteristics such as the present invention makes full use of the characteristics of sapphire graphical substrate, and it is low that the nitride epitaxial film of acquisition has dislocation density, and the surface is a minute surface, and the XRD half-breadth is low.And adopting this method to carry out nitride epitaxial, growth window is wide, is applicable to high-quality nitride epitaxial film commercialization growth.

In addition, the figure format diameter of sapphire graphical substrate of the present invention is 1.5 μ m～3 μ m, and spacing is 0.5 μ m～1.5 μ m, highly is 1 μ m～2 μ m.

The figure format diameter of preferred sapphire graphical substrate is 2 μ m, and spacing is 1 μ m, highly is 1 μ m.

Description of drawings

Fig. 1 is the generalized section of sapphire graphical substrate.

Fig. 2 is in sapphire graphical substrate low temperature growth buffer layer generalized section.

Fig. 3 is through after crystallization, forming the seed crystal generalized section at sapphire graphical substrate low temperature growth buffer layer.

Fig. 4 is the generalized section that GaN forms through first step island growth at the sapphire graphical substrate.

Fig. 5 is the generalized section of GaN at the closed continuous epitaxial film that forms of sapphire graphical substrate.1 is the Sapphire Substrate figure, and 5 is continuous GaN epitaxial film.

The practical implementation case

Utilize MOCVD equipment (31 business PCs of the Crius of Aixtron company), adopting diameter D is that 2 μ m, figure interval S are that 1 μ m, figure height H are 1 μ m sapphire graphical substrate 1, as shown in Figure 1.

The GaN low temperature buffer layer of at first growing, growth temperature is 530 ℃, forming thickness in sapphire graphical substrate 1 one sides at last is the low temperature buffer layer 2 of 30nm.As shown in Figure 2.

Elevated temperature to 1030 ℃ carries out crystallization again, nucleation on the sapphire graphical substrate then.As shown in Figure 3, on Sapphire Substrate 1, form seed crystal 3.

Reduce the temperature to 990 ℃, the mol ratio of control Ga and N is 675 ︰ 1, and growth time is 1000s, makes GaN carry out sufficient island growth shape at extension pattern 4, does not cross the figure top of Sapphire Substrate 1, and its pattern is as shown in Figure 4.

Then elevated temperature to 1040 ℃, the mol ratio of control Ga and N is 1200 ︰ 1.This moment, GaN was in the two-dimensional growth pattern, was main with cross growth, and closed at Sapphire Substrate 1 top, formed continuous GaN epitaxial film 5, and is as shown in Figure 5.

The GaN epitaxial film surface that obtains does not have little hole for minute surface, and (002) that XRD measures and (102) half-breadth explain that all less than 300arcsec crystal mass is good.Carry out the growth window test through adjusting growth temperature up and down; Three dimensional growth and two-dimensional growth temperature raise 20 ℃ and reduce by 20 ℃ simultaneously simultaneously; Other growth parameter(s)s are constant; All can obtain the high quality GaN epitaxial film, prove and adopt this method epitaxial growth GaN epitaxial film to have very wide growth window, temperature window is greater than 40 ℃.

Above-mentioned case study on implementation described a kind of on the sapphire graphical substrate method of epitaxial growth nitride epitaxial film.The method makes full use of the characteristics of sapphire graphical, and control GaN three dimensional growth and two-dimensional growth on sapphire graphical reduce dislocation, discharge stress.And this method overcome the characteristics of conventional growth technique extension GaN growth temperature window narrows on sapphire graphical, is highly suitable for commercially producing, and improves product stability.

Claims

1. the method for epitaxial growth nitride epitaxial film on the sapphire graphical substrate is characterized in that may further comprise the steps:

3) be that 500～1200 ︰ 1, growth temperature are that 900 ℃～1020 ℃, pressure are under the condition of 300～600mbar in the mol ratio of Ga and N, growth 500s～2000s;

4) be that 1000～2000 ︰ 1, growth temperature are that 1020 ℃～1070 ℃, pressure are under the condition of 100～500mbar in the mol ratio of Ga and N, growth 100s～4000s.

2. according to the said method of claim 1, the figure format diameter that it is characterized in that said sapphire graphical substrate is 1.5 μ m～3 μ m, and spacing is 0.5 μ m～1.5 μ m, highly is 1 μ m～2 μ m.

3. according to the said method of claim 2, the figure format diameter that it is characterized in that said sapphire graphical substrate is 2 μ m, and spacing is 1 μ m, highly is 1 μ m.