CN1832112A

CN1832112A - Method for changing polar of gallium nitride epitaxial layer grown by hydride vapour phase epitaxy method

Info

Publication number: CN1832112A
Application number: CN 200610024155
Authority: CN
Inventors: 雷本亮; 于广辉; 齐鸣; 叶好华; 孟胜; 李爱珍
Original assignee: Shanghai Institute of Microsystem and Information Technology of CAS
Current assignee: Shanghai Institute of Microsystem and Information Technology of CAS
Priority date: 2006-02-24
Filing date: 2006-02-24
Publication date: 2006-09-13

Abstract

This invention relates to a method for altering the pole of GaN epitaxial layer grown by HVPE characterizing in applying a method of interrupting HCl growth, which first of all penetrates NH3 to nitride the Sapphire under high temperature then penetrates HCl to grow GaN, this time, the GaN film surface shows N pole, then closes HCl after growing for a period of time and continues NH3 for 1-60min, then opens the HCl to grow GaN film continuously and operates like this for 2-10 times, the pole of GaN turns to Ga of a smooth surface from a rough N pole surface and the dislocation density is reduced and the crystal quality is increased.

Description

A kind of method that changes the polar of gallium nitride epitaxial layer of grown by hydride vapour phase epitaxy method

Technical field

The present invention relates to the method for a kind of change hydride gas-phase epitaxy (HVPE) method growing gallium nitride (GaN) epitaxial loayer polarity.Be intended to improve the epitaxial growth GaN film quality, belong to technical field of material.

Technical background

The application of III group-III nitride semiconductor photoelectric material device more and more widely, but six side's phase III group-III nitrides are the very strong crystal of a surface polarity.Because its single shaft and non-centrosymmetry structure show spontaneous polarization and piezoelectric effect [H.Morkoc, Nitride Semiconductors and Devices, Springer, Heidelberg, 1999].When material epitaxy forms heterojunction, even do not having under the situation of stress, because the both sides, interface have different spontaneous polarization effects and will occur a large amount of polarization charges at the interface, cause that thus very strong internal electric field will influence the electronics of material [O.Ambacher et al.J.Appl.Phys.V85 strongly, 3222,1999] and optical property [F.Widmann et al.Phys.Rev.B V58, R15989,1998].The polarity field of III group-III nitride heterojunction had not only depended on the orientation of crystal but also had depended on the result who adopts after the different resilient coating technology along direction of growth growth.When growing, GaN do not have the same atom stacking order with substrate on substrates such as sapphire, GaAs, Si, [0001] direction of GaN epitaxial loayer may be parallel to the direction of growth but also may be opposite with the direction of growth as a result, will cause two kinds of different polarity thus: Ga polarity or N polarity.

The film of these two kinds of polarity has diverse structure and electrical properties [E.S.Hellman, MRSInternet J.Nitride Semicond.Res.V3,11,1998].Also stable [the X.Q.Shen et al.Appl.Phys.Lett.V77 of more smooth its chemical property in the surface of Ga polarity film, 4013,2000], has lower impurity density (Al, O, C etc.) [M.Sumiya et al.Appl.Phys.Lett.V76,2098,2000], also be easier to obtain p type doping [L.K.Li et al.Appl.Phys.Lett.V76,1740,2000].The film of Ga polar surfaces has higher Schottky barrier and also lower [the Z.Q.Fang et al.Appl.Phys.Lett.V78 of its leakage current, 2178,2001], also has more excellent optical property [S.F.Chichibu et al.Appl.Phys.Lett.V78,28,2001].Therefore the film that generally speaking has the Ga polar surfaces has more excellent quality than the film with N polar surfaces.Yet a large amount of research all only concentrates on the character of observing or study Ga polarity or N polarity.People such as W.Zhang once adopted the method for growth interruption to discharge the epitaxially grown stress of GaN and reduced dislocation density [the W.Zhang et al.Appl.Phys.Lett. of GaN film, V78,772,2001], but how the material transition of N polarity is rarely had report for Ga polarity.

Summary of the invention

The object of the present invention is to provide the method for a kind of change hydride gas-phase epitaxy (HVPE) growing GaN epitaxial loayer polarity.

Specifically, prepare in the process of GaN film at HVPE, Al is adopted in the growth of GaN ₂O ₃, among GaAs, SiC and the Si any one as substrate, at high temperature logical earlier NH ₃To Al ₂O ₃Carry out nitrogenize etc. a kind of substrate, make the surface form the nucleation that very thin AlN island structure helps GaN.Then logical HCl gas is grown, and the GaN film surface that grow out this moment presents N polarity.Close HCl gas after growth a period of time, and NH ₃Gas flow circulates always, and remains unchanged.Then continue to open HCl gas and grow, close HCl gas again after a period of time and keep NH ₃Gas flow is constant, repeated multiple times like this, and the GaN material that obtains will be the stable Ga polarity of smooth surface and chemical property by shaggy N reversing.Repeatable operation interruption of growth 2-10 time continues NH ₃Gas 1-60 minute, NH ₃Reacting gas is with N ₂, H ₂Or both mists are as carrier gas, and the temperature of interruption of growth is 900-1100 ℃, and cracking provides nitrogen (N) atom under the high temperature, make the surface of the GaN film in the growth that structure again take place, thereby change Ga polarity into.This method is simple, adopts when being suitable for scientific experiment and batch process.

The GaN epitaxy layer thickness with N polar surfaces of initial growth is 0.5-20 μ m; The GaN epitaxial loayer with N polar surfaces of initial growth of the present invention does not just adopt HVPE also can adopt a kind of method preparation in metal organic chemical vapor deposition, molecular beam epitaxial method or the laser pulse, and it is not identical entirely just to prepare actual conditions.

As mentioned above, adopt the method for interruption of growth to change the polarity that the GaN material is grown, its advantage is summarized as follows:

1. when interrupting HCl, will be for providing adequate time because lattice mismatch and thermal coefficient of expansion differ the release of the too big stress that causes;

2. when interrupting HCl, because NH is constantly arranged ₃Supply, structure again will take place in the GaN surface, change the condition that provides for realizing the material growth polarity; Described NH ₃Reaction gas flow is 400-600sccm, the reversing of the too big or too little all unfavorable GaN growth of flow;

3. the grow out surface dislocation density of GaN material of the method for adopt interrupting HCl only is 1 * 10 ⁷/ cm ²About, thereby the performance of the device of raising made;

4. only adopted NH during interruption of growth ₃Reacting gas and N ₂Or H ₂Carrier gas can not introduced contaminating impurity;

5. the method for interruption of growth is simple, and cost is low, easily uses in industrial production;

Description of drawings

Fig. 1 .HCl interruption of growth process schematic diagram, abscissa is time (branch), ordinate is HCl flow (sccm).

Fig. 2. the GaN surface (a) in hydride gas-phase epitaxy equipment after the HCl interruption of growth 4 times and should the surface through H ₂SO ₄: H ₃PO ₄Surface topography (b) behind=3: 1 solution (250 ℃) the corrosion 10min, directly on sapphire Grown GaN surface topography (c) and should the surface through H ₂SO ₄: H ₃PO ₄Surface topography (d) behind=3: 1 solution (250 ℃) the corrosion 10min, all pictures all adopt AFM to measure, and area is 10 * 10 μ m.

Embodiment

Embodiment 1

Method provided by the invention is used for the polarity that HVPE changes the growth of GaN material, and Al is adopted in the growth of GaN ₂O ₃As substrate, at first at high temperature logical NH ₃To Al ₂O ₃Substrate carries out nitrogenize 7min, NH ₃Flow be 500sccm, make the surface form the nucleation that very thin AlN island structure helps GaN.Then logical HCl gas is grown, and the GaN film surface that grow out this moment presents N polarity.Behind the growth 30min, the thickness of GaN film is 10 μ m, then closes HCl gas, and reacting gas NH ₃And H ₂Or N ₂The gas flow of carrier gas remain unchanged, this process is 20min.Continue to open the HCl gas 20min that grows then, then close HCl gas 20min again, 4 times so repeatedly, the GaN material that obtains will be the stable Ga polarity of smooth surface and chemical property by the N reversing, and its crystalline quality also improves a lot.Growth temperature is 1000 ℃ in the present embodiment.

Present embodiment HCl interruption of growth 4 times, with the GaN film of direct growth and the surface topography after being corroded separately as shown in Figure 2.

Fig. 2 (a) is the GaN surface after the interruption of growth 4 times, and roughness is 0.527nm, and is very smooth, and presents the step-flow growth pattern of two dimension.This surface is through H ₂SO ₄: H ₃PO ₄Its surface topography smoother still changes little (Fig. 2 (b)) behind=3: 1 solution (250 ℃) the corrosion 10min, and roughness is 1.066nm,, show that it is difficult for being corroded, chemical property is highly stable, illustrates that promptly the GaN film after the interruption of growth is Ga polarity.Fig. 2 (c) is the GaN epi-layer surface of direct growth, and is comparatively smooth, and its roughness is 2.214nm, obvious variation (Fig. 2 (d)) has taken place in its surface after being corroded, it is more coarse to have become under the naked eyes, presents the etch pit that many diameters are about 1 μ m, and roughness is 35.536nm.This explanation is directly at Al ₂O ₃The surface of substrate Grown GaN film more easily is corroded, and chemical property is unstable, promptly directly at Al ₂O ₃The Grown GaN epitaxial loayer is N polarity on the substrate.By to two kinds of samples the variation of corrosion front and rear surfaces pattern as can be seen the HCl interruption of growth help to change the polarity of GaN film.

Embodiment 2

The Si substrate is adopted in the GaN growth, adopt the method shown in the embodiment 1 to interrupt the HCl growth, interruption times is 8 times, and each time is 10min, the N polar GaN film thickness of growth is 20 μ m, and the interruption of growth temperature is that the GaN material surface dislocation density of 950 ℃ of Ga polarity that obtain is 1 * 10 ⁷/ cm ²All the other are similar with embodiment 1.

Embodiment 3

Adopt the GaAs substrate, adopt molecular beam epitaxy accretion method growth N polar GaN material, it interrupts 900-1100 ℃ of growth temperature, interruption times 2-10 time, and each duration is 1-60min, NH ₃For reaction gas flow is 500-700sccm, carrier gas is N ₂And H ₂Mist.The surface dislocation density of resulting GaN material is 1 * 10 ⁷/ cm ², surface roughness only is 0.527nm (similar to embodiment 1).

Claims

1. method that changes the GaN epitaxial loayer polarity of hydride gas phase epitaxial growth, GaN growth are at high temperature logical NH ₃Substrate is carried out nitrogenize, carry out the GaN film that growing surface presents N polarity by HCl gas again, close HCl gas after a period of time that it is characterized in that growing, and NH ₃Gas flow remains unchanged, and then continues to open HCl gas and grows, and closes HCl gas again after in the time of one section and keeps NH ₃Reaction gas flow is constant, interrupts the HCl growth operation so repeatedly 2-10 time, continues NH ₃The gas time is 1-60 minute, and the GaN film that makes the surface present N polarity is changed into ganoid Ga polarity; Described HCl gas growth time is 10-30min.

2. press the method for the GaN epitaxial loayer polarity of the described change hydride gas phase epitaxial growth of claim 1, it is characterized in that described backing material is Al ₂O ₃, among GaAs, SiC and the Si any one.

3. press the method for the GaN epitaxial loayer polarity of the described change hydride gas phase epitaxial growth of claim 1, it is characterized in that helping the GaN nucleation at surface formation AlN island structure behind the underlayer nitriding.

4. press the method for the GaN epitaxial loayer polarity of the described change hydride gas phase epitaxial growth of claim 1, NH when it is characterized in that repeatedly interruption of growth ₃Reacting gas is with N ₂, H ₂Or both mists are as carrier gas.

5. press the method for the GaN epitaxial loayer polarity of the described change hydride gas phase epitaxial growth of claim 1, it is characterized in that described interruption of growth temperature is 900-1100 ℃.

6. press the method for the GaN epitaxial loayer polarity of the described change hydride gas phase epitaxial growth of claim 1, it is characterized in that the Grown GaN film thickness is 0.5-20 μ m.

7. press the method for the GaN epitaxial loayer polarity of the described change hydride gas phase epitaxial growth of claim 1, it is characterized in that continuing NH ₃Reaction gas flow is 400sccm-600sccm.

8. by the method for the GaN epitaxial loayer polarity of the described change hydride gas phase epitaxial growth of claim 1, it is characterized in that adopting the surface dislocation density of GaN material of the Ga polarity of the method growth of interrupting HCl is 1 * 10 ⁷/ cm ²

9. press the method for the GaN epitaxial loayer polarity of any described change hydride gas phase epitaxial growth of claim in the claim 1,2,4 or 6, be applicable to the reversing of the N polar GaN that adopts metal organic chemical vapor deposition molecular beam epitaxial method or the preparation of laser pulse method.