CN102146585A

CN102146585A - Non-polar surface GaN epitaxial wafer and preparation method of non-polar surface GaN epitaxial wafer

Info

Publication number: CN102146585A
Application number: CN201110001970XA
Authority: CN
Inventors: 陈莉; 陈霞; 熊辉
Original assignee: WUHAN HUGE OPTOELECTRONICS CO Ltd
Current assignee: WUHAN HUGE OPTOELECTRONICS CO Ltd
Priority date: 2011-01-04
Filing date: 2011-01-04
Publication date: 2011-08-10

Abstract

The invention discloses a non-polar surface GaN epitaxial wafer. A non-polar GaN film is synthesized and grown on a sapphire substrate by using a metal organic chemical vapor deposition (MOCVD) system, and the film comprises a low-temperature buffer layer grown on the sapphire at one time and an alpha surface GaN film. Different epitaxial structures of light emitting diodes, laser devices, solar cells and the like are grown on the film in different periods. The growth of the non-polar alpha surface GaN material can be effectively controlled, and the quantum efficiency and the luminous efficiency in the periods can be improved.

Description

Nonpolar face GaN epitaxial wafer and preparation method thereof

Technical field

The present invention relates to the semiconductor material preparation field, especially a kind of nonpolar face GaN epitaxial wafer and preparation method thereof.

Background technology

The main flow substrate of present commercial GaN thin film epitaxial growth is the c surface sapphire crystal. usually, the Grown GaN film is the growth of c direction of principal axis along its polar axis on the c surface sapphire substrate, film has spontaneous polarization and piezoelectric polarization effect, cause the powerful built in field of the inner generation of film, reduced the luminous efficiency of GaN film widely.In addition, polarized electric field also brings a serious problem: along with the increase of injecting electric current, bigger blue shift also can take place in the luminous peak position of diode.

One of scheme that solves is a growth cubic structure nitride heterojunction.Theory shows that the wurtzite gan is not have spontaneous polarization in vertical [0001] symmetry axis direction.If have shear stress in growth plane inside simultaneously, the piezoelectric polarization effect on these directions of son is not said existence yet so.In recent years, the scientific research personnel is just considering that the direction of growth is the quantum yield that so-called nonpolar GaN film improves film perpendicular to the c axle.The substrate of epitaxy nonpolar GaN film mainly is r face (0112) surface sapphire and γ-LiAlO ₂Though γ-LiAlO ₂(100) face and GaN (1100) face lattice match good (average lattice mismatch be 1.4%), but γ-LiAlO ₂There is serious component volatilization during crystal growth, is difficult to obtain large-sized crystal, and the crystal facile hydrolysis, thermostability is bad, and these shortcomings have greatly limited γ-LiAlO ₂The development of substrate.It is good that sapphire crystal has physical and chemical performance, and Heat stability is good obtains advantages such as large size and low price easily.Though sapphire and GaN lattice mismatch and thermal mismatching are bigger, but updating and improve along with Sapphire Substrate processing technology and GaN epitaxial growth technology, the technology of extension GaN film is ripe day by day on Sapphire Substrate, at present reported first such as successful commercialization .Craven on r (0112) surface sapphire growing nonpolar GaN film, because lattice mismatch is bigger, the film quality of growth is relatively poor, defective more (mainly being dislocation and fault).Along with the improvement of thin film epitaxy technology, at present to make the X-ray scanning peak width at half height of the nonpolar GaN film that the substrate growth obtains be 0.29 ° to the r surface sapphire, and dislocation desity is 2.6 * 10 ¹⁰Cm-2, stacking fault density are 3.8 * 10 ⁵Cm ^-2, mean roughness is 0.46nm, the luminous efficiency of GaN film obviously improves.

Summary of the invention

The object of the present invention is to provide a kind of nonpolar face GaN epitaxial wafer, this epitaxial wafer can solve above-mentioned r face non-polar GaN epitaxy quality problems, and purpose in addition of the present invention provides a kind of method with metal organic chemical vapor deposition system (MOCVD:Metal-Organic Chemical Vapour Deposition) the nonpolar a face GaN film of technology hetero epitaxy on sapphire.

Technical scheme of the present invention is: a kind of nonpolar face GaN epitaxial wafer, nonpolar GaN film utilize MOCVD system synthetically grown on Sapphire Substrate, and this film is included in last low temperature growth buffer layer of sapphire and a face GaN film.A kind of preparation method of nonpolar face GaN epitaxial wafer may further comprise the steps: step 1: in the MOCVD system, at N ₂Protection is warmed up to 700 ℃, growing low temperature Al on Sapphire Substrate down _0.15Ga _0.85The N buffer layer, the V/III ratio is 6000, low-temperature protection pressure 200 torrs, TMGa flow 64SCCM, TMAl flow 36SCCM; Step 2: be warmed up to 1050 ℃, growth a face GaN, TMGa flow 64SCCM.Growing nonpolar face GaN thin-film material is used to the different epitaxial structure of growing, and at photodiode, laser apparatus is used on the solar cell.

The invention has the advantages that: the present invention can control the growth of nonpolar a face GaN material, quantum yield and luminous efficiency during can improving effectively.

Description of drawings

Fig. 1 is the growth result figure of non-polar GaN epitaxial wafer of the present invention;

Fig. 2 is the X ray 2 θ/ω test result of non-polar GaN epitaxial wafer of the present invention;

Fig. 3 is the X ray rocking curve peak width at half height test result of non-polar GaN epitaxial wafer of the present invention.

Embodiment

Below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in more detail.

A kind of preparation method of nonpolar face GaN epitaxial wafer may further comprise the steps: growth one deck buffer layer on substrate; Growth a face GaN film on buffer layer; Further, described substrate is the r surface sapphire substrate; Further, described buffer layer is the Al of metal organic source vapour phase epitaxial growth _0.15Ga _0.85N, wherein the Al source is a trimethyl aluminium, and the gallium source is a trimethyl-gallium, and hydrogen is as carrier gas; Further, when described deposition buffer layer, growth temperature is 700 ℃, and the V/III ratio is 6000, and thickness is 20nm.

Please refer to Fig. 1, the r face list of exempting to clean is polished the growth room that Sapphire Substrate is put into metal organic source vapour phase epitaxy (MOCVD) material growing system, slowly be warmed up to 1200 ℃, the baking substrate reduces the temperature to 700 ℃ after 5 minutes, the V/III ratio is 6000, the Al of growth 20nm _0.15Ga _0.85The N buffer layer.Slowly be warmed up to 1050 ℃ then, at NH ₃After atmospheric condition was annealed 15 minutes down, the GaN of growth 1.5um.

With this method in addition the GaN epitaxial wafer belong to (11-20) non-polar GaN, the sample that is obtained by above step is carried out test analysis.Fig. 2 is the X ray 2 θ/ω test result of non-polar GaN epitaxial wafer of the present invention.X ray 2 θ/ω test result result shows to have only narrow Al ₂O ₃(1-102), Al ₂O ₃(2-204), the existence of GaN (11-20) diffraction peak is not found (0001), (10-11) waits other dephasigns, has proved crystal property preferably.Fig. 3 is the X ray rocking curve peak width at half height test result of non-polar GaN epitaxial wafer of the present invention.The twin crystal halfwidth of the X ray rocking curve of epitaxial wafer is about 0.19 °, has shown result preferably.Fig. 4 is scanning electronic microscope (the SEM:scanning electron microscope) surface topography map of non-polar GaN epitaxial wafer of the present invention.As seen film surfacing for lattice defects such as discovery twist irregularities, reaches the basic demand of LED device.The nonpolar preferably r face of the quality GaN epitaxial wafer that above-mentioned these results surface the present invention can get at the r surface sapphire.

Above example of making is half embodiment of the present invention, and making method adoptable production program in last century is a lot, and all equalizations of doing according to claim of the present invention change and modify, and all should belong to covering scope of the present invention.

Claims

1. nonpolar face GaN epitaxial wafer, nonpolar GaN film utilizes metal organic chemical vapor deposition system synthetically grown on Sapphire Substrate, it is characterized in that: this film is included in the last growing low temperature Al of sapphire _0.15Ga _0.85N buffer layer and a face GaN film.

2. the preparation method of a nonpolar face GaN epitaxial wafer may further comprise the steps: step 1: in the MOCVD system, at N ₂Protection is warmed up to 700 ℃, growing low temperature Al on Sapphire Substrate down _0.15Ga _0.85The N buffer layer, the V/III ratio is 6000, low-temperature protection pressure 200 torrs, TMGa flow 64SCCM, TMAl flow 36SCCM; Step 2: be warmed up to 1050 ℃, growth a face GaN, TMGa flow 64SCCM.

3. according to the described a kind of nonpolar face GaN epitaxial wafer of claim 1, it is characterized in that: growing nonpolar face GaN thin-film material is used to the different epitaxial structure of growing, and at photodiode, laser apparatus is used on the solar cell.