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k ICROSCE DEFECT KINETICS IN MELT-UONN GRAS(U) 1/1 MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF MATERIALS I SCIENCE AND ENGINEERING H C GATOS ET AL. 31 AUG Of UNCLRSSIFIED MSi99f4-3-K-4561 F/I 2/12 ML -~~~~~12 2 a *M S*, OW 1, 2. * ~'ROCOPY RI,[u1O)N Tt!l H * *~...***. * *-*-.. * % ~. - -.% *.. **%*..*.% Ln TO: OFFICE OF NAVAL RESEARCH ARLINGTON, VIRGINIA Final Technical Report.- For Period 1 August 1983 to 31 August 1986 on MICROSCALE DEFECT KINETICS IN MELT-GROlsN GaAs Contract NOO!L-83-K-0581 Submitted by Frofessor Farrv C. Gates - a. % Dr. Jacek Losi.- Depart7ent cf a.eriais Science and 7ngne r :: ch.-::s s:itute of echncoz v CaFbridfge, a -c e::s J'1 t~ 17 ,8-3 It.; :... :...*. ; :;.:...: *:..... *: :: :. :. :.:: :.:..).. b. h*.mm:u.m.:.i :.;bi:) h: m b mil: -w~w~r Wtv ~'U IOur I. SVMARY OF WORK ACCOMPLISHIED research on the kinetics of defects in melt-grown GaAs involved crystal growth experiments and post-growth treatments of crystals co-mbined ourxtnsv chsara1tgrwt exper o et weusdropetisrla oi onuteddfcs It exeniv chartactriztio ofpe letroi prosdanepeisrlated cntor fcts. Czocralki-ypepuller equipped with a vertical magnetic field for the growth of GaAs under conditions of suppressed convection. We have identified for the first tlime a beneficial effect of the magnetic field on the compensation ratio and electron mobility (Refc. 1). I.Experiments on doping with oxygen is of GaAs c-,-al grown b'; the Horizontal Bridg-man technique have revealed an anomalous silicon se-- r egation behavior governed by chemical reactions in a closed growth annul rather than standard impurity distribution during the solidification (Refs. 2and 3). 7x- erim~ents on fast growth of GaAs by the LEG techniqu e using pulling rates of ud to 2 i nch/hn showed a S4cnl cat 6crease o' 712 concentratiodn w-tn 4 cea~ the nulling rate. k-e rave Snow n tnat tnfs etteort crfcinn:c rcast Cooling of the cry-stal c-ro-.7i undcer high pu 11ing~ rates (Ref..) vhe have essent-ily conpleted' a detailed std:-nte effects or 71astlo defornation on d.eer) levels in Cos(FEfs. 5,-'). 7his tuycor hinea T e a ndcti cna T ic e r zat(-7 c or,,- s s *e c E2st CC ce 4r-tc at T~~howdco:tr to 7reon )elief that n-da leves wore 1-troacce-.t or srat s at ahc - :ab-ove th*-e vli e n -e Fad w'-.1ichcu ue C, an -. ~... ~C % %~ -2- GaAs Growth in a Magnetic Field A series of GaAs crystals were grown in our laboratory using the LEC V apparatus with a magnetic field parallel to the crystal growth axis. As shown in Fig. 1, the portion of the crystal grown without a magnetic field exhibits pronounced striations revealed by depth profiling of differentiilly etched crystals and by cathodoluminescence scanning. The magnitude of inhomogeneities decreased with increasing magnetic field. The effect of a magnetic field on the macroscopic properties of LEC GaAs are tummarized in Table I, and they are also presented in Fig. 2. It is evident that portions of GaAs grown in a magnetic field of 3500 Oe have higher mobilitv values and lower compensation ratios than those grown without a r,-aznetic field. The results of a magnetic field on GaAs propertier established in the course of this study will be discussed extensively in a Ph.D. thesis (Ref. 1) currently under preparation..ncorporation of Oxvcen and Silicon during HB Growth of GaAs Oxvoen. hns -rofcund effects on the key electronic prcert4es and point defects of CaAs crvstals. 7-hus, when added in the Frowth s.s ten, it decreases t..e free c toc.rcn conce-tricn a e:,nces the cc--nraticn of deep donors 4n oe rent: tnc r a :. ). We have studied the incororat ion of - ~~~~~~~~..., -?,: },r:'::'.ri,-a net:.c. -lvn :ve t i'. :., ;7 i t.i..,-.:.e- r ea e t -~ et Oc oityite... iv e. c er e ec 'e cc7,~.tt ' S: -.,....a -e r c. ee e d to -* ~ * a~ *~**. *.~. ~p *. -: ~ ~ ~ -D*ep ~ 7 ~ Jl ~ J p ~ clha lu. in esec J~~V~Fh 13-0,O Ot FAA17 r zj-: For i4a.. L~2 ty Cde CA I -4- TABLE I Effect of Magnetic Field on 5 Properties of LEC-GaAs iagnticlectron Electron Faneic Mobility Concentration -ild3 Cunmpensation (0e) (cmv)(c ) Ra t io E E E E E16.76 or-. % 5 Y TP ; JrT -T, k-k WNb. V- W- h-- -bs 1. b L 4W 0 0u tcd Ici L LO UL C) U I41S~dO (1) Q.).7 Lf -6- These results showed that oxygen and silicon incorporation during GaAs growth is controlled by the chemical eqilibrium rather than by qtandard impurity distribution during solidification. The results outlined above are currently being prepared for publication (Ref. 3). Deformation-Induced Defects in GaAs We have completed a detailed study of the effects of plastic deformation on electrical and optical propetties of GaAs. Employing DLTS we have found no appreciable increase in the concentration of the main deep donor EL2 (see Fig. 3). However, we have also found (using optical DLTS) deformation-introduced hole traps of an activation energy E v ev (see Fig. 4). These hole traps act as acceptor levels and they are responsible for the removal of free electrons upon plastic deformation. Detailed results of this study~ will be presented -in a forthcoming publication (Ref. 6). I!. INDEX OF REFERENCES I.L.X. Pawlowicz, Evolution of: Defects in, LEC-GaAs, Ph.D. Thesis, I7T, 1987, under preparation. 2. H.C. Gates, M. Skowrons-ki. L. Pawlowicz and j. Lacowski, 'Oxvoen in GaAs: Ziect and Tn- etefcs nt hs of S er. 7,A 15) 3. J. Lagovski. D.G. Li and 1H.C. Gatos, 'Kncorocrato_n of Ch.vzen and Sili-4con :.~-rcr ~~sc ~tas. retentnt- a: Ist Ccnf. cf- :rri'a n.. S.C. Gatos jnd JL ski, : a n el ated DE Cts i-nga--h ene in in- 7-C' - l l ci 1 i c_ i_ 7.ct' 5I %P -7-8. W. Walukiewicz, Le Wang, L. Pawlowicz, J. Lagowski and H.C. Gatos, Effect of Deep Level Ionization on Low Temperature Electron Mobility in SI GaAs, 5eri-Insulating 111-V Materials, Kah-nee-ta 1984, edited by D.C. Look and J.S. Blakemore, Shiva Publishing, Ltd., Nantwich, England, III. INDEX OF REPORTS 1. Publications/Patents/Presentations/ionors Report - 1 October 1983 through 30 September l Annual Progress Report for Period 1 August to 31 July 19S5 3. Publications/Patents/Oresentations/ionors Report - 1 October 19S'. through 30 September Final Technical Report for Period 1 August 1983 to 31 August 1986 I If) U o U I I LU H 0 It) ~ -~ 2~~~-) I ILIt C). Lr4) 3 _73 LAI d-, I *1~ J.4.
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