利用MOCVD在r面蓝宝石上生长的a面GaN中两步AlN缓冲层的优化_英文

第32卷 第4期2011年4月

发 光 学 报

C H I N ESE J OURNAL OF LUM I N ESCENCE

V ol 32N o 4

A pr .,2011

Artic le I D :1000 7032(2011)04 0363 05

Optim ization of Two step A lN Buffer of a plane

Ga N Film s Grown on r plane Sapphire byMOCVD

H E Tao ,CHEN Y ao ,L IH ui,DA I Long gu i,WANG X iao li,

XU Pe i qiang,WANG W en x i n *

,CHEN H ong

(Be i jing N ationa lL abora t ory of Cond e n se d M a tter ,In stit u t e of P hy sics ,

C hinese Acad e my o f S cie n ces ,B eiji ng 100190,Ch i na )

Abst ract :N onpo l ar (1120)a p l ane G aN fil m s w ith t wo step A l N buffer(a lo w te m perature (LT )and a h i gh te m perat u re (HT )A l N lay ers)we re g rown on (1102)r plane sapph i re by m eta l organ ic chem ical vapor depo siti on (M OCVD ).T he as g rown fil m s w ere i nvesti g ated by h i gh reso l ution X ray diffracti on (XRD )and pho t o l um inescence (PL ).T he t w o step A l N bu ffer has been proved t o be advantageous i n crysta l quality compared w it h one step LT G a N o r HT A l N buffers i n our ea rl y w orks .In this repo rt ,the t h ickness of t he t w o step buffer w as f u rt her opti m ized ,and much less an isotropic a p l ane G aN fil m s w ere achieved .

It w as f ound t hat t he LT A l N layer o f the t w o step buffer

p l ayed a key role i n reducti on of an i so tropy of the G aN fil m gro w n .K ey words :G a N;aniso tropy ;XRD;A l N ;buffer layer

CLC nu m ber :O 472;O482 31 PACS :71 55 Eq ;78.55.Cr PACC :7155F ;7855E Docum en t code :A DO I :10.3788/fgxb20113204.0363

R ecei ved date :2011 01 20;R ev i sed date :2011 02 07

Foundati on ite m:Project s upported by t he N ati onalNatura l Science Foundation of Ch i na (60890192,60877006,50872146);

t he Ch i n ese

Science and Technology M i n i stry ( 863 ,No .2009AA033101)

Bi ography :HE Tao ,born i n 1982,m al e ,H ub eiP rovi n ce .H is w ork focuses on co m pound se m i condu ctorm aterial s .

E m ai:l b lizz ardcas @s i na .co m,Te:l (010)82649053

*:C orres pondi ng Author ;E m ai:l w x w ang @aphy .iphy .ac .cn,Te:l (010)82649208

1 Introducti on

Ga N based se m iconductors have attracted much attenti o n for their successful applicati o n in optoelec tron ics as e m issi o n w ave length rang ing fro m green to ultrav io l e t due to theirw ide band gap

[1 8]

.H owever ,conventional (0001)c p lane quantum w e ll struc tures i n Ga N based optoelectron ic dev ices suffer fro m t h e quantu m confine m en t Star k effect due to the ex istence o f strong piezoe lectric and spontaneous po lar izations

[9 12]

.These fields can spatially separate electr ons and holes in t h e quan t u m w e lls and reduce t h e overlaps o f their w ave f u nctions ,resu lti n g in re ducti o n of t h e reco m binati o n effic iency and red shift of the e m ission w avelengths i n li g h t e m itti n g de vices .One o f the pr o m ising m et h ods to eli m inate po larizati o n i n duced electric field effects is to gro w

group n itri d e layers i n d irecti o ns per pend icular to t h e [0001]c ax i s where t h ere is no polarization field perpendicu l a r to the layer i n terfaces

[13 23]

.

H o w ever ,the difficulty i n g r ow i n g these non po lar gr oup nitri d e epilayers lies in the anisotropy of i n plane strai n and ato m diff u sion length [13,15]

.U sually a

LT Ga N

[13]

or aHT Al N

[18]

layer was used as t h e buffer

layer for the gro w th o f a plane Ga N on a r p lane sapph ire substrate .M any other g roups g re w a p lane Ga N w ith ep itax ia l latera l over g ro w th (ELO )

[15 16]

.

H o w ever ,the a plane Ga N gro w n still exh i b its obv i ous an iso tropy and is far fro m high perfor m ance po larizati o n free dev ices .The t w o step A l N buffer w as proved to be advan tageous i n cr ystal quality i n our early wo r ks

[14]

.I n th is repo r,t w e opti m ized the

t h ickness of the t w o step A l N buffer f u rther and achieved m uch less anisotrop i c a p lane Ga N fil m s .

364

发 光 学 报第32卷2 Experi m ents

Nonpo lar a plane Ga N fil m s w ere gro w n on r

plane sapph ire substrates by a lo w pressure,ro tating

disk MOCVD syste m.The5.08c m(2 i n ch)sub

strate w as co mm erc i a ll y availab l e and requ ired no ex

situ preparati o n befo re loading i n to reactor.A fter

loadi n g,the substrate w as i n itiall y treated in a hy

drogen a m b i e n t at1100 for10m i n,then the

t w o step A l N buffer w as gro wn under a reactor pres

sure o f1.1 104Pa(gro w t h para m eters i n details

sho wn in Tab le1),fi n ally a1.5 m th ick Ga N fil m

w as g r own w ith a gro w t h rate o f2.0 m/h and a

/ rati o of1200.T ri m ethy l g a lli u m(TMGa),

tri m ethyla l u m inu m(TMA l)and a mm onia(NH3) w ere used as t h e precursors for the Ga,A,l and N sources,respecti v e l y.H ydrogen w as used as the carrier gas.The as gro w n sa m ples w ere characte rized by HRXRD and PL.HRXRD m easure m en ts w ere carri e d out fo r eva l u ating the crystalli n e qua lity and i n p l a ne str uctural an isotropy,usi n g a B ede D1 high reso l u ti o n double ax is diffracto m eter.PL w as dispersed w ith a0.5m m onochro m ator and detected by a photo m ultiplier tube at a l o w te m perature o f 28K to assess the crysta l quality.A10mW H e Cd laser w as used as the excitation source.

Table1 G ro w th para m eters of the t w o step A l N buffer for sa mp les A,B and C

LT A l N HT A l N

t/ d/n m t/ d/n m A80001100400

B800401100400

C800801100400

3 R esults and D iscussion

HRXRD m easure m ents w ere carried out to eva l u ate the structura l an iso tropy of the as g r own sa m ples.The experi m ental geo m etry o f the HRXRD sy mm etry scan is sho w n i n Fig.1(a).Defi n e the azi m uth ang le as zero w hen the pro jecti o n of the i n c i d ent bea m is paralle l to the[0001]c ax is,w ith o f 90 correspondi n g to the m ax is.By ro tating t

h e sa m ple fro m-180 to180 w ith an i n cre m enta l

step of15 ,the F WHM of a plane Ga N X ray sy m m etric scan as a function o f azi m ut h ang le w as m easured,as sho w n in Fig.1(b).Sa m ple A exhibits obv ious anisotropy,reaching a m ini m um F WHM o f 0.222 a l o ng the c ax is and a m ax i m u m of0.430 along the m ax is.For sa m ple B,t h e anisotropy is less pronounced,reachi n g a m ini m um of0.192 along the c ax i s and a m ax i m um of0.306 along the m ax is,as repo rted in our early w orks[14].Sa mp le C sho w s a c lear reduced anisotropy,reach i n g a m ini m um o f0.208 along t h e c ax is and a m ax i m um o f 0.245 a l o ng the m ax is.The upper and lo w er li m it values of t h e F WHM for the three sa m ples are sho wn i n Fig.1(c).Compari n g t h e three sa m p les,as the

F ig.1 (a)T he exper i m enta l geome try o f t he azi m uth depen

dence HRXRD sy mme try scan,defi n i ng t he azi

m uth ang l e as zero when the pro jecti on of t he i nc i

dent beam is para llel to the c ax i s;(b)T he F WHM o f

a p l ane G a N X ray symm etr ic scans o f sa m ples A,

B and

C as a f uncti on o f t he azi m uth angle ;(c)T he

FWHM of a p l ane G a N X ray sy mme tr i c scans

a l ong t he c ax is and t he m ax i s for sa m ples A,B

and C.

第4期HE T ao ,et al :O pti m i zati on of Two step A l N Buffer o f a p lane G a N F il m s 365

t h ickness o f the LT A l N layer increases ,the F WHM val u e along the m ax is decrease rap i d ly w ith that along the c ax i s varies sli g htly ,i n d icating a clear

reducti o n of structura l an isotropy .

The PL spectra of the as gro wn t h ree sa m ples m easured at 25K w ere sho w n i n Fig .2.The strong e m issi o n locating at 3.426e V assoc i a tes w ith struc tura l defects ,and particu larly ,the i n tensity of t h is peak w as found to re late w it h the density of t h e basa l plane stacking fau lts

[21 23]

.A ccor d i n g to t h e results

of L iu et al .and Paskov et al .,the 3.3e V peak i n vo lves i m purities ,w hich decorate the partia ld isloca ti o ns ter m i n ating t h e basa l plane stacking faults .The 3.21e V peak m ay re l a te to the DAP of G a N.The w ide peak at the energy of 3.475e V be l o ngs to the near band edge e m ission (NBE )of a plane Ga N,and co m prises t w o peaks ,arisi n g fro m reco mb i n ation of free exc itons and excitons bound to shallo w neu tra l donors

[21 23]

,respecti v e l y .The i n tensity of NBE

of sa m ple C w as found to be m uch stronger than that of sa m p les A and B ,suggesti n g a high qua lity o f sa mp le C

.

F ig .2 PL spec tra of t he samp l es m easured at 25K

As w e kno w,because of the different ato m ic arrange m ents ,t h e m i g rati o n ability of Ga along the c ax is is m uch stronger than that along the m ax is ,resu lti n g i n better cr ystal qua lity that of a l o ng the c ax is for a plane Ga N

[13,15]

.I n our experi m ents ,the

i n troduction of t w o step buffer layer ,especia lly LT A l N layer ,p lays a key role in the reducti o n o f struc tura l anisotr opy o f the gro w n a p l a ne G a N.B ecause at l o w te m perature ,

t h e ato m ic m i g ration ability o f

A lw as m uch lo w er than t h at of Ga and A l at high te mperatures ,w hich would reduce the d ifference o f ato m ic m igration ability bet w een the c ax is and the m ax is .The HT A l N l a yer gro w n on t h is LT A l N layer is of high qua lity ,w hich prov i d s a te mp late for the gro w th o f the fo ll o w ing a plane Ga N [14]

.So

t h e a plane Ga N gro w n w it h the t w o step A l N buffer

is o f reduced an isotropy and h i g h quality .

Consi d eri n g sa m ples B and C ,the increase o f t h e LT A l N th ickness cou l d f u rther suppresse the ato m ic m i g rati o n ability along the c ax i s and favor t h at a l o ng the m ax is ,leadi n g to an i n crease o f the F WHM va l u e along t h e c ax is and an decrease o f t h at a l o ng the m ax is i n a plane Ga N.

4 Concl usi on

N onpo lar a p lane Ga N fil m s w ith a t w o step A l N buffer w ere gro w n on r p lane sapph ire by MOC VD .The thickness o f the t w o step buffer w as opti m ized .a plane Ga N fil m s w ith m uch less an iso t ropy and better quality w ere ach i e ved co m pared w ith our prev i o us w ork .

It w as found t h at t h e LT A l N

layer o f the t w o step buffer played a key role i n the m i prove m ent of crystal quality for the gr o w th of Ga N.

R eferences :

[1]N aka mu ra S .T he ro le o f struct ura l i m per fecti ons in In G aN based bl ue li ght e m itti ng d i odes and L aser d i odes [J].Science ,

1998,281(5379):956 961.

[2]A s ifK han M,Bhatta ra iA,K uz n ia J N,et al .H i gh electron mob ilit y transist o r based on a G aN A l x G a 1-x N he tero j

uncti on [J].A pp l .Phy s .L ett .,1993,63(9):1214 1215.

[3]M o rko c H,Strite S ,G ao G B ,et al .La rge band gap Si C , n itride ,

and ZnSe based se m i conducto r dev ice

techno log ies [J].J.App l .P hy s .,1994,76(3):1363 1398.

[4]N akamura S ,Senoh M,M uka i T.H ighly p typedM g doped G aN fil m s g rown w ith G a N bu ffer layers [J].Jpn.J.App l .

P hy s .Pa rt 2,1991,30(10A ):L 1708 L1711.

366

发 光 学 报第32卷

[5]W ang M ingyue,Yuan Ji nshe,Yu G uohao.Co rre l a ti on o f the y ell ow pho t o lu m i nescence and exc itati on sources of G aN fil m

g rown by M OCVD[J].Ch i n.J.Lu m i n.(发光学报),2009,30(1):73 76(in Chi nese).

[6]W u D i anzhong,W angW enx i n,Y ang Cheng liang,et al.In A s quantu m dots w ith InG a A s Cap l ayer i nfrred detec t o r gro w n by

M BE[J].Chin.J.Lu m in.(发光学报),2009,30(2):209 213(i n Ch i nese).

[7]Y ang Chenli ang,Y e H u i q,i W ang W enx in,et al.Effect of i nterface gro w th i nterrupti on on sp i n re l axation i n G aA s( )

A l G aA s/G aA s quant um w e lls[J].Ch i n.J.Lu m i n.(发光学报),2009,30(2):214 218(i n Ch i nese).

[8]X ing B i ng,CaoW enyu,D uW e i m in.T e m perature dependen t PL of In G aN/G a N mu lti ple quantu m w e lls w ith va riab l e con

tent of In[J].Chin.J.Lu m in.(发光学报),2010,31(6):864 869(i n Chinese).

[9]I m J S,K o ll me r H,O ff J,et al.R educ ti on of osc ill a t o r strength due to p i ezoe lectr i c fi e l ds i n G aN/A l

x G a

1-x

N quant um

w ells[J].Phy s.R ev.B,1998,57(16):R9435 R9438.

[10]Lang er R,Si m on J,O rti z V,et al.G ian t electr i c fi e l ds i n unstra i ned G aN si ng l e quant um w ells[J].A pp l.Phy s.L ett.,

1999,74(25):3827 3829.

[11]Le febvre P,M ore lA,G allartM,et al.H i gh i nterna l electr ic fi e l d i n a graded w i dth In G a N/G a N quantu m w e l:l accura te

deter m i nation by ti m e reso l ved pho tolu m i nescence spectroscopy[J].App l.Phy s.L ett.,2001,78(9):1252 1254. [12]Bernard i n iF,F i o renti n iV.M acro scop ic po lar i za ti on and band o ffsets at nitride he tero j unc ti ons[J].Phy s.Rev.B,1998,

57(16):R9427 R9430.

[13]L iD S,Chen H,Y u H B,et al.A n i sotropy of a plane G a N gro w n on r plane sapph ire by m e talorg an i c che m ical vapo r

depo siti on[J].J.C ry st.G ro w th,2004,265(1 2):107 110.

[14]Y an J F,Guo L W,Zhang J,et a l.Cha racter istics of t he i m prov ed a plane G a N fil m s g rown on r plane sapph ire w i th t wo

step A l N buffer layer[J].J.Cryst.Grow th,2007,307(1):35 39.

[15]W ang H M,Chen C Q,G ong Z,et al.An i sotropic structura l characteristi cs of(1120)G a N te mplates and coa l esced epitax i a l

l ateral overgrown fil m s deposit ed on(1012)sapphire[J].App l.Phys.Lett.,2004,84(4):499 501.

[16]H ira m atsu K,N ishiya m a K,M otoga ito A,et al.R ecent prog ress i n se l ective a rea grow th and epitax i a l latera l overg row th o f

nitri des:effects o f reactor press u re i n M OVPE gro w t h[J].Phy s.Stat.Sol.(a),1999,176(1):535 543.

[17]A rak iM,M ochi m izo N,H osh i no K,et al.D irect gro w th o f a plane G a N on r plane sapphire s ubstra te by m eta l organ ic

vapor phase epitaxy[J].Jp n.J.A pp l.Phy s.,2007,46(2):555 559.

[18]N iX,Fu Y,M oon Y T,et al.O pti m iza ti on of(1120)a p l ane G aN g row th by M OCVD on(1102)r p lane sapph ire[J].

J.Cryst.Grow th,2006,290(1):166 170.

[19]H o llander,J H,K appers M J,M c A leese C,et al.I m provements in a plane G a N crysta l qua lity by a t wo step g row th

process[J].App l.P hy s.Lett.,2008,92(10):101104 1 3.

[20]C ravenM D,L i m S H,W u F,et al.Structura l characteriza ti on o f nonpo lar(1120)a plane G a N t h i n fil m s grown on

(1102)r plane sapph i re[J].App l.Phy s.L ett.,2002,81(3):469 471.

[21]P askov P P,Sch ifano R,M onem ar B.E m ission properties of a plane G aN gro w n by m e tal organ ic che m ica l vapor depo si

tion[J].J.A pp l.Phys.,2005,98(9):093519 1 7.

[22]L i u R,BellA,Ponce F A,et al.Lu m i nescence from stacking fau lts i n g alli um n itride[J].A pp l.Phy s.L ett.,2005,86

(2):021908 1 3.

[23]N etze la C,W ern i ckea T,Z e i m e ra U,et al.N ear band edge and de fect em issions from ep itax ia l latera l ove rgrown a p l ane

G a N w it h d ifferent stripe or ientations[J].J.C ry st.G ro w th,2008,310(1):8 12.

第4期HE T ao,et al:O pti m i zati on of Two step A l N Buffer o f a p lane G a N F il m s 367

利用MOCVD在r面蓝宝石上生长的

a面GaN中两步A lN缓冲层的优化

何 涛,陈 耀,李 辉,戴隆贵,王小丽,徐培强,王文新*,陈 弘

(中国科学院物理研究所凝聚态国家重点实验室,北京 100190)

摘要:采用两步A l N缓冲层(一层低温A l N和一层高温A l N)在r面蓝宝石衬底上生长了非极性的a面G aN,并利用高分辨X射线衍射和光致荧光谱对所生长的材料进行了研究。两步A l N缓冲层在我们之前的工作中已被证明比单步高温A l N或低温G a N缓冲层更有利于减小材料各向异性和提高晶体质量,本文进一步优化了两步A l N缓冲层的结构,并得到了各向异性更小,晶体质量更好的a面G aN薄膜。分析表明,两步A l N缓冲层中的低温A l N层在减小各向异性中起着关键作用。低温A l N层能抑制了优势方向(c轴)的原子迁移,有利于劣势方向(m轴)的原子迁移,从而减小了A l原子在不同方向迁移能力的差异,并为其后的高温A l N缓冲层和G a N层提供 生长模板 ,以得到各向异性更小、晶体质量更好的a面G aN材料。

关 键 词:G a N;各向异性;X射线衍射;A l N;缓冲层

中图分类号:O472;O482 31 PACS:71.55.Eq;78.55.Cr PACC:7155F;7855E 文献标识码:A

文章编号:1000 7032(2011)04 0363 05

DO I:10.3788/fgxb20113204.0363

收稿日期:2011 01 20;修订日期:2011 02 07

基金项目:国家自然科学基金(60890192,60877006,50872146);科技部 863 计划(2009AA033101)资助项目

作者简介:何涛(1982-),男,湖北黄冈人,主要从事化合物半导体材料的研究。

E m ai:l b li zzardcas@sina.co m,T e:l(010)82649053

*:通讯联系人;E m ai:l w xwang@aphy.i 0b13e4efe009581b6bd9eb5f,Te:l(010)82649208

发光学报 成为美国 EI 收录源期刊

2010年3月25日, 发光学报 接到E I中国信息部通知:从2010年第1期起正式被 E I ( 工程索引 )收录为刊源。

E I作为世界领先的应用科学和工程学在线信息服务提供者,是全世界最早的工程文摘来源,一直致力于为科学研究者和工程技术人员提供最专业、最实用的在线数据、知识等信息服务和支持。 发光学报 进入E I收入系统,对加强我国发光学研究领域及论文作者开展更广泛的国内外交流,提升我国技术人员学术声誉具有积极的促进作用。

发光学报 由中国物理学会发光分会、中国科学院长春光学精密机械与物理研究所主办,徐叙瑢院士和范希武研究员任名誉主编,申德振研究员担任主编。 发光学报 自1980年创刊以来,业内专家的大力支持下,得到了健康、快速的发展。 发光学报 2010年度影响因子为1.12,已成为我国物理学领域有较大影响的学术刊物。

发光学报 能够进入 E I ,是国际社会对工作在发光学科研领域里的我国科学工作者学术水平的认可,是对长春光机所主办期刊的认可。 发光学报 成为 E I 源期刊后,将获得更好的办刊平台,为将 发光学报 办成有特色的精品期刊创造了良好的条件。

本文来源：https://www.bwwdw.com/article/gvvl.html