CN100547735C

CN100547735C - Utilize uniform nano particle dot array mask to improve the method for thick film GaN quality

Info

Publication number: CN100547735C
Application number: CNB2008100424592A
Authority: CN
Inventors: 王新中; 于广辉; 林朝通; 曹明霞; 巩航; 齐鸣; 李爱珍
Original assignee: Shanghai Institute of Microsystem and Information Technology of CAS
Current assignee: Dahom (Fujian) Illumination Technology Co., Ltd.
Priority date: 2008-09-03
Filing date: 2008-09-03
Publication date: 2009-10-07
Anticipated expiration: 2028-09-03
Also published as: CN101350298A

Abstract

The present invention relates to a kind of method of utilizing uniform nano particle dot array to improve thick film GaN quality, it is characterized in that adopting the SiO of nanometer scale ₂, SiO or Si _xN _yIn dot matrix as the GaN epi-mask.Before hydride gas-phase epitaxy, earlier electron beam evaporation layer of metal Al on the GaN template adopts electrochemical method to generate cellular anodised aluminium (AAO) again, then the medium of injection lattice structure in the hole, remove AAO then, then obtained equally distributed SiO on the template ₂The lattice structure of nano particle places template epitaxial growth in the reaction chamber at last.Because the selectivity of vapour phase epitaxy will begin to select to be grown in SiO ₂On the zone outside the dot matrix, connect into complete GaN film through the transversal epitaxial growth process at last.Reduced the dislocation density of epitaxial loayer, and dislocation density distributes evenly, improve the utilizability of thick film greatly.Method is simple, has omitted the complicated technology of photoetching, and mask size is narrowed down to nanometer scale, is suitable for producing in batches.

Description

Utilize uniform nano particle dot array mask to improve the method for thick film GaN quality

Technical field

The present invention relates to a kind of method of utilizing uniform nano particle dot array mask to improve thick film GaN quality.The preparation field that belongs to the GaN material.

Background technology

The GaN material possesses good characteristics such as high-luminous-efficiency, high heat conductance, high temperature resistant, radioresistance, acid and alkali-resistance, high strength and high rigidity, in recent years, as state-of-the-art semi-conducting material in the world and get most of the attention, can be made into efficient indigo plant, green, purple, white light-emitting diode and laser, obtained more applications and concern.Yet GaN still relies on Al at present ₂O ₃, GaAs, SiC, foreign substrate such as Si, because the lattice mismatch and the thermal expansion mismatch coefficient of they and GaN material are all very big, in the GaN of extension material, there are bigger stress and higher dislocation density, the performance and the life-span of having reduced the GaN device widely inevitably.Because the dissociation pressure of nitrogen is very high, is difficult to utilize high growth temperature to obtain large-sized GaN body monocrystalline.And HVPE growth rate height, equipment is simple, preparation cost is low, is acknowledged as the most promising preparation GaN self-supporting substrate technology in recent years, thereby has attracted domestic and international researcher's extensive interest.People adopt this method successfully to prepare thick film GaN substrate [R.J.Molnar et al.J.Cryst.Growth before this, V178,147,1997], but the development that dislocation density is higher, the characteristics of luminescence is relatively poor, very easily problem such as cracking is still perplexing the self-supporting substrate technology, for this reason, people have carried out a lot of exploratory developments.Comprising typical horizontal extension outgrowth (ELOG) technology [T.S.Zheleva et al.Appl.Phys.Lett., V78,772,2001], make defect concentration reduce by 3～4 orders of magnitude, reach＜10 ⁶Cm ^-2Hitachi, Ltd adopts Void-Assisted Separation (VAS) technology promptly to form TiN film [the Yuichi OSHIMA et al.Jpn.J.Appl.Phys.V 42 of holey on GaN template, L1,2003], thus make defect concentration be reduced to 5 * 10 ⁶Cm ^-2Also have a lot of methods that reduce dislocation density in addition, all be to be similar to the ELOG technology, but mostly need technologies such as photoetching, process complexity and cost are higher, and traditional photoetching method is difficult to prepare the mask arrangement of nanoscale, dislocation density distributes also very inhomogeneous, has limited effective utility ratio of epitaxial loayer greatly.Therefore, become very important and urgent for the research of equally distributed nanoscale mask, and in HVPE growing GaN thick film, utilize SiO ₂Nano particle dot array mask reduces material growth defect density, is a kind of novelty and obvious results method.So far, rare report.

Summary of the invention

The object of the present invention is to provide a kind of method of utilizing uniform nano particle dot array mask to improve thick film GaN quality.It is characterized in that:

(1) mask is SiO ₂The nanometer particle dot matrix;

(2) SiO ₂Nano particle dot array is to be deposited on Al ₂O ₃, among SiC, Si or the GaAs on any one substrate on the Grown GaN epitaxial loayer template;

(3) SiO ₂Nano particle dot array is to utilize electrochemical method corroding metal Al to generate cellular anodised aluminium (AAO) layer, then deposition one deck SiO in the hole ₂And form.

Specifically, before HVPE (hydride gas-phase epitaxy) preparation GaN thick film, adopt Al ₂O ₃SiC, any substrate among Si or the GaAs, utilize HVPE, the GaN epitaxial loayer that metal organic chemical vapor deposition (MOCVD) or the growth of molecular beam epitaxy (MBE) method are one 0.1～300 micron is as template, electron beam evaporation or sputtering method deposit layer of metal aluminium (Al) thin layer again, thickness is about 50nm～1 μ m, afterwards (18-25 ℃) under its room temperature placed oxalic acid (0.3mol/L) or sulfuric acid (15wt%) solution to carry out electrochemical corrosion, phosphoric acid (5wt%) solution of putting into 25-40 ℃ again soaks the mesh structural porous anodic aluminum oxide film that 30-40min has just formed rule, utilizes electron beam evaporation to inject one deck medium SiO again in the hole ₂Layer is removed AAO with acid solution then, can form equally distributed SiO at the GaN template surface ₂The lattice structure of nanometer scale particle, the medium SiO of the lattice structure that forms ₂Yardstick be the 5-100nm magnitude.As real nanoscale mask in the epitaxial growth.But the medium of formation lattice structure is SiO or Si also _xN _y, also be the magnitude of 5-100nm.Then template is placed HVPE equipment growing GaN thick film, anneal gas is N ₂, H ₂Perhaps both mists.Because the selectivity of vapor phase epitaxial growth, in the growth course, GaN will begin to select to be grown in SiO ₂In the GaN template zone between the nano particle, and can be at SiO ₂Grow on the mask, connect into complete GaN film through the transversal epitaxial growth process then, realized the nanoscale horizontal extension outgrowth of GaN material thus.The dislocation that part results from the GaN template will directly be subjected to SiO ₂The inhibition of mask, thus greatly reduce the dislocation density of extension thick film GaN material, thus improved the quality of GaN film.And because SiO ₂Nano particle dot array distributes very evenly on entire substrate, so dislocation distributes also quite evenly in HVPE Grown GaN epitaxial loayer, and unlike traditional horizontal extension outgrowth, dislocation density is very big in the subregion, the subregion is very little.So preparation method provided by the invention has also improved the utilizability of thick film GaN material, the method for transversal epitaxial growth is any one among employing HVPE, MOCVD or the MBE on the nano particle dot array mask.Method provided by the invention is simple, for SiO ₂Evaporation equipment requires also not high, adopts when being suitable for scientific experiment and batch process.

As mentioned above, this method adopts SiO ₂Nano particle dot array is as mask horizontal extension outgrowth GaN material, and its advantage is summarized as follows:

1. in the AAO hole, evaporate SiO ₂Form equally distributed nano particle dot array structure, thereby made the epitaxially grown mask of GaN, realized the horizontal extension outgrowth, therefore reduced dislocation density, improved crystal mass;

2. the used gas of annealing atmosphere can not introduced contaminating impurity;

3.AAO preparation less demanding, and electrochemical corrosion course is simple, realizes volume production easily;

4. the SiO of Xing Chenging ₂It is quite even that nano particle dot array distributes, and the size of particle and spaced apartly also can carry out free adjustment with the need;

5.SiO ₂Character is highly stable, can not introduce contaminating impurity;

6. owing to SiO as mask ₂Therefore nano particle dot array size and at interval evenly extends in the GaN epitaxial loayer dislocation density and distributes also comparatively evenly, and this has also improved the utilizability of thick film GaN greatly;

7. metal inserting layer of the present invention is deposited on Al ₂O ₃, among SiC, Si or the GaAs on any one the substrate on the Grown GaN epitaxial loayer, can adopt HVPE, gas phase epitaxy of metal organic compound (MOCVD) or molecular beam epitaxy common methods such as (MBE) as the GaN outer layer growth method of template.

Description of drawings

The structural representation of the thick film GaN of Fig. 1 method preparation provided by the invention.

Among the figure, 1.Al ₂O ₃Substrate; 2.GaN epitaxial loayer; 3.SiO ₂Nano particle dot array mask; 4.HVPE Grown GaN thick film.

(102) face x diffraction pattern that the sample A of Fig. 2 preparation and conventional method prepare sample B.

Embodiment

Embodiment 1. is used for HVPE and prepares the thick film GaN material.

As shown in Figure 1, adopt the MOCVD method at Al ₂O ₃The about 3 microns GaN films of growth on substrate (0001) face, with this film as the HVPE template, then under 200 ℃ temperature, the method that adopts electron beam evaporation is in the thick metal Al thin layer of template surface deposition 300nm, again the template that has the Al layer is put into oxalic acid solution (0.3mol/L), at room temperature adopt 40 volts voltage to carry out the about 15min of anodic oxidation, then metal A l is etched electrochemically into the porous AAO of regular distribution, and then place template 30 ℃ of phosphoric acid solutions (5wt%) to soak 40min, purpose is to enlarge the aperture and remove that part of aluminium oxide that the aperture bottom contacts with the GaN of lower floor, deposits the thick SiO of 5nm after cleaning up in nano-pore ₂, in 20% hydrochloric acid solution, soak 60min at last, remove the AAO layer, can form equally distributed SiO at template surface ₂Nano particle dot array structure, these dot matrix will be taken as the mask of thick film GaN growth.Then template is put into the hvpe reactor chamber, at N ₂Atmosphere is warming up to 800 ℃, begins logical NH ₃The GaN layer of protection template begins logical HCl grow (Fig. 2 A) in the time of 1050 ℃.In order to prove the validity of the method, in the HVPE growing system, place the dull and stereotyped MOCVD-GaN template (any processing is not passed through on its surface) of another sheet, another sheet thick film GaN material (Fig. 2 B) of growing simultaneously. measure by X-ray diffraction, 102 of show sample A half-peak breadth only is 214.5arcsec as a result; And 102 the half-peak breadth of sample B to be this result of 319.2arcsec. show: adopt this method growth to reduce dislocation density in the GaN epitaxial loayer greatly, significantly improved the quality of crystal.In addition, by the measurement of room temperature PL spectrum, the peak of sample A also is the twice of sample B by force, and the result also illustrates and adopts SiO ₂Behind the nanometer particle dot array mask, the optical characteristics of epitaxial loayer GaN thick film obviously improves; And the peak position value of sample A and sample B corresponds respectively to 3637

With 3630

The red shift phenomenon has taken place, and has illustrated that the method also can help the epitaxial loayer Stress Release.

Embodiment 2.

With SiC, Si or GaAs is substrate, and the dielectric layer that injects in the anodised aluminium hole is SiO or Si _xN _y, preparation thick film GaN processing step is identical with embodiment 1.

Claims

1, a kind of method of utilizing uniform nano particle dot array mask to improve thick film GaN quality is characterized in that:

(1) with Al ₂O ₃, SiC, Si or GaAs be substrate, the GaN epitaxial loayer of the one deck of growing thereon earlier is as template;

(2) on the template of the GaN epitaxial loayer that step 1 prepares, deposition layer of metal Al thin layer;

(3) template is adopted electrochemical method Al is oxidized to the mesh structural porous anodised aluminium that is evenly distributed;

(4) template is put into phosphoric acid solution and removed that part of aluminium oxide that the aperture bottom contacts with the GaN of lower floor and the size that changes the hole;

(5) one deck dielectric layer that reinjects in the anodised aluminium hole, described dielectric layer is SiO, SiO ₂Or Si _xN _y

(6) then remove the porous anodic aluminium oxide layer, on the GaN template surface, form the lattice structure of equally distributed nanometer scale particle with acid solution;

(7) the nanometer scale particle dot matrix that utilizes formation at last carries out hydride gas phase transversal epitaxial growth thick film GaN as mask.

2, by the described method of utilizing uniform nano particle dot array mask to improve thick film GaN quality of claim 1, it is characterized in that at Al ₂O ₃, on SiC, Si or the GaAs substrate, growth is to adopt in hydride gas-phase epitaxy, metal organic chemical vapor deposition or the molecular beam epitaxial method any one as the GaN epitaxial loayer of template.

3,, it is characterized in that the thickness as the GaN epitaxial loayer of template is the 1-300 micron by claim 1 or the 2 described methods of utilizing the uniform nano particle dot array mask to improve thick film GaN quality.

4,, it is characterized in that metal A l film adopts electron beam evaporation or sputtering method to prepare on the GaN template by the described method of utilizing uniform nano particle dot array mask to improve thick film GaN quality of claim 1; The thickness of metal A l film is 50nm-1 μ m.

5, by the described method of utilizing uniform nano particle dot array mask to improve thick film GaN quality of claim 1, it is characterized in that metal A l film oxidation is that mesh structural porous anodised aluminium is that to place the oxalic acid solution of 0.3mol/L or mass percentage concentration earlier be that 15% sulfuric acid solution carried out anodic oxidation in 15 minutes, and then to put into mass percentage concentration be that 5% phosphoric acid solution soaked 40 minutes.

6, by the described method of utilizing uniform nano particle dot array mask to improve thick film GaN quality of claim 1, the yardstick that it is characterized in that described formation lattice structure dielectric layer is the 5-100nm magnitude.

7, by the described method of utilizing uniform nano particle dot array mask to improve thick film GaN quality of claim 1, it is characterized in that nano particle dot array makes mask, the method for hydride transversal epitaxial growth is to adopt in hydride gas-phase epitaxy, metal organic chemical vapor deposition and the molecular beam epitaxial method any one.

8,, it is characterized in that prepared GaN thick film is made up of the GaN epitaxial loayer on substrate, the substrate, the lattice structure of equally distributed nanometer scale on the GaN epitaxial loayer and the GaN thick film of transversal epitaxial growth by the described method of utilizing uniform nano particle dot array mask to improve thick film GaN quality of claim 1; The dielectric layer of the lattice structure that forms is SiO ₂, SiO or Si _xN _y