Ud W. hl Epitaxy of Semiconductors Intrdtn t hl rnpl 4) Springer Contents 1 Introduction 1 1.1 Epitaxy 1 1.1.1 Roots of Epitaxy 1 1.1.2 Epitaxy and Bulk-Crystal Growth 4 1.2 Issues of Epitaxy 4 1.2.1 Convention an Use of the Term "Atom" 4 1.2.2 Assembly of Atoms 5 1.2.3 Tasks for Epitaxial Growth 6 References 9 2 Structural Properties of Heterostructures 11 2.1 Basic Crystal Structures 11 2.1.1 Notation of Planes and Directions 11 2.1.2 Wafer Orientation 13 2.1.3 Face-Centered Cubic and Hexagonal Close-Packed Structures 13 2.1.4 Zincblende and Diamond Structures 14 2.1.5 Rocksalt and Cesium-Chloride Structures 16 2.1.6 Wurtzite Structure 16 2.1.7 Thermal Expansion 17 2.1.8 Structural Stability Map 19 2.1.9 Polytypism 20 2.1.10 Random Alloys and Vegard's Rule 21 2.1.11 Virtual-Crystal Approximation 26 2.2 Elastic Properties of Heterostructures 26 2.2.1 Strain in One and Two Dimensions 26 2.2.2 Three-Dimensional Strain 27 2.2.3 Hooke's Law 29 2.2.4 Poisson's Ratio 31 2.2.5 Pseudomorphic Heterostructures 2 2.2.6 Critical Layer Thickness 35 v viii Contents 2.2. Apprh t Extnd th Crtl hn 39 2.2.8 rtll lxd r nd hrl Mth 42 2. ltn 44 2.. Ed nd Sr ltn 4 2..2 ltn tr 46 2.. ltn n th f Strtr 4 2..4 ltn n th nd nd nblnd Strtr 4 2.. ltn Enr 51 2..6 ltn n th hp nd Wrtzt Strtr 4 2.. M Crtl 57 2.4 Strtrl Chrtrztn Un ffrtn 8 2.4. r 8 2.4.2 h Strtr tr 59 2.4. h prl tt 6 2.4.4 h Eld Cntrtn 6 2.4. hltn Sn n th prl Sp 64 2.4.6 prlSp Mp 6 2. rbl Chp. 2 0 2.6 Gnrl dn Chp. 2 73 frn 4 3 Eltrn rprt f trtrtr 79 . l rprt 79 .. Eltrn nd f nblnd nd Wrtzt Crtl . 79 ..2 Strn Efft 8 .. prtr pndn f th ndp 8 ..4 ndp f All 88 .2 nd Offt 0 .2. EltrnAffnt l 91 .2.2 CnAnn l 2 .2. Mdl f p Iprt vl 93 .2.4 Intrfpl hr 95 .2. MdlSld hr 6 .2.6 Offt f S Ivlnt trtrtr 97 .2. nd Offt f trvlnt Intrf 97 .2.8 nd Offt f All 0 . Eltrn Stt n nnl Strtr 0 .. nnlt f th Eltrn ntfStt 02 ..2 Chrtrt Sl fr Sz Qntztn 06 .. Qnt Wll 0 ..4 Qnt Wr 2 .. Qnt t 6 .4 rbl Chp. 2 . Gnrl dn Chp. 2 frn 2 Contents ix 4 hrdn f Eptxl rGrth 131 4. h Elbr 131 4.. hrdn Elbr 2 4..2 Gbb h l 4 4.. Gbb Enr f SnlCpnnt St 135 4..4 h ndr n SnlCpnnt St 139 4.. rvn r fr Crtllztn 40 4..6 Cpnnt St 4 4.2 Crtlln Grth 48 4.2. n hrnnl ltn 48 4.2.2 trn hrnnl ltn 2 4.2. Grth Md 4 4.2.4 Elbr Srf 155 4.2. nnl ltn 6 4.2.6 Ilnd Grth nd Cln 64 4.2. Grth tht ltn 66 4.2.8 pnn r Aftr Grth Intrrptn 68 4. rbl Chp. 4 68 4.4 Gnrl dn Chp. 4 6 frn 6 5 Att Apt f Eptxl rGrth 171 . Srf Strtr 171 .. h Kn St f Kl Crtl 2 ..2 Srf f Kl Crtl 173 .. lxtn nd ntrtn 175 ..4 EltrnCntn Mdl 6 .. nttn f Srf ntrtn 179 ..6 ntrtn f th GA(00 Srf 8 .. h Sln (( x ntrtn 84 .2 Knt r Stp n r Grth 86 .2. Knt n th rrStpKn Mdl 86 .2.2 Att r n ltn nd Grth 88 .2. Adt n rrd Srf 2 .2.4 Grth b Stp Advn 4 .2. h EhrlhShbl rrr 197 .2.6 Efft f th EhrlhShbl rrr n Srf Stp 199 .2. hnn f Srf Stp 20 .2.8 Grth f S(I( x Srf 204 .2. Grth f GA(00 ß2(2 x 4 Srf 20 . Slfrnzd ntrtr 20 .. StrnKrtn Ilnd Grth 20 ..2 hrdn r Knt n Ilnd rtn 2 .. Wr Grth n nplnr Srf 2 x Contents 5.4 Problems Chap. 5 220 5.5 General Reading Chap. 5 221 References 221 6 pn, ffn, nd Cntt 225 6.1 Doping of Semiconductors 225 6.1.1 Thermal Equilibrium Carrier-Densities 226 6.1.2 Solubility of Dopants 231 6.1.3 Amphoteric Dopants 235 6.1.4 Compensation by Native Defects 236 6.1.5 DX Centers 239 6.1.6 Fermi-Level Stabilization Model 241 6.1.7 Delta Doping 243 6.2 Diffusion 247 6.2.1 Diffusion Equations 247 6.2.2 Diffusion Mechanisms 250 6.2.3 Effective Diffusion Coefficients 252 6.2.4 Disordering of Heterointerfaces 255 6.3 Metal-Semiconductor Contact 259 6.3.1 Ideal Schottky Contact 259 6.3.2 Real Metal-Semiconductor Contact 263 6.3.3 Practical Ohmic Metal-Semiconductor Contact 265 6.3.4 Epitaxial Contact Structures 267 6.4 Problems Chap. 6 270 6.5 General Reading Chap. 6 271 References 271 7 Mthd f Eptx 275 7.1 Liquid-Phase Epitaxy 276 7.1.1 Growth Systems 277 7.1.2 Congruent Melting 279 7.1.3 LPE Principle 281 7.1.4 LPE Processes 283 7.2 Metalorganic Vapor-Phase Epitaxy 286 7.2.1 Metalorganic Precursors 287 7.2.2 The Growth Process 290 7.2.3 Mass Transport 293 7.3 Molecular Beam Epitaxy 299 7.3.1 MBE System and Vacuum Requirements 300 7.3.2 Beam Sources 302 7.3.3 Uniformity of Deposition 307 7.3.4 Adsorption of lmpinging Particles 309 7.4 Problems Chap. 7 310 7.5 General Reading Chap. 7 311 References 311 Cntnt x Appndx Anr t rbl 315 Indx 3 19 ndntl hl Cntnt 325.