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Behavior of lattice defects in GaAs
Vol. l, No. 5
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
23. JAHN-TW~.T.k~ DISTOETIONS INDUCED BY TETRASEDRAL-SITE Fe2+ IONS. J.B. Goodenough (Lincoln Laboratory*, M~ssachusetts Institute of Technology, ton 73, i~ssachusetts, U.S.A.).
125
Lexing-
The Jahn-Teller effect for tetrahedral-site Fe 2÷ ions is expressed to secondorder in the interaction energy and to lowest-or~er anharmonic vibrational energies. The formal results are identical to those for ~ 3 ÷ or Cu 2+ ions in octahedral sites. However, interpretation of the parameters that enter the for~1 expressions shows that the mode and transition temperature of any static, crystalline distortion is much more strongly influenced by long-range elastic coupling in the case of tetrahedral-site Fe2+ ions. This result is used to interpret the absence of a static distortion from cubic sy~netry in the spinel Fe[AI~O~, for the occurrence of tetragon~ (c/al) in chromium and vanadium spinels containing tetrahedral-site Fe ~+ ions, and for the complex crystallographic properties of the system Fe3.xCrx04. (Received 5 September 1963)
24. BEHAVIOR OF LATTICE DEFECTS IN GaAs. J. Blanc, R.H. Bube & L.R. Weisberg (RCA Laboratories, Princeton,
New Jersey, U.S.A.)
Single crystalline samples of GaAs grown by either the horizontal Bridgman (HB) or floating zone (FZ) technique have been annealed in the range 4~30-80OOC, us,~ally for periods of 16 hr in either the presence or absence of copper. Measurements of thermally stimulated currents, dark conductivity, density, and thermal conductivity were carried out on samples at various stages of annealing. It was found that very large concentrations of traps (>lO19 cm-3) can be introduced by annealing, and these are identified as lattice defects. It is proposed that there are two defects, a donor and an acceptor which occur both paired and isolated in the lattice. When paired, their ionization energies are roughly 0.2 eV, and x~hen isolated are roughly 0.5 eV. There is a fundamental difference between FZ and HB crystals in annealing characteristics and of greatest significance, at 700oc in the absence of copper, the concentration of defects increases in FZ samples and decreases in HB samples. This indicates that the defects are not present in therm~3 equilibrium. Instead, the defects are probably introduced by an accident of growth during the growth process, in a neutral form such as a precipitate or antiphase domain. Copper acts as a catalyst in enhancing the rate of defect annealing. (Received 6 September 1963)
*Operated ~clth support from the U.S. Army, Navy and Air Force.
ABSTRACTS OF PAPERS TO APPEAR IN J. PHYS. CHEM. SOLIDS
23. JAHN-TW~.T.k~ DISTOETIONS INDUCED BY TETRASEDRAL-SITE Fe2+ IONS. J.B. Goodenough (Lincoln Laboratory*, M~ssachusetts Institute of Technology, ton 73, i~ssachusetts, U.S.A.).
125
Lexing-
The Jahn-Teller effect for tetrahedral-site Fe 2÷ ions is expressed to secondorder in the interaction energy and to lowest-or~er anharmonic vibrational energies. The formal results are identical to those for ~ 3 ÷ or Cu 2+ ions in octahedral sites. However, interpretation of the parameters that enter the for~1 expressions shows that the mode and transition temperature of any static, crystalline distortion is much more strongly influenced by long-range elastic coupling in the case of tetrahedral-site Fe2+ ions. This result is used to interpret the absence of a static distortion from cubic sy~netry in the spinel Fe[AI~O~, for the occurrence of tetragon~ (c/a
24. BEHAVIOR OF LATTICE DEFECTS IN GaAs. J. Blanc, R.H. Bube & L.R. Weisberg (RCA Laboratories, Princeton,
New Jersey, U.S.A.)
Single crystalline samples of GaAs grown by either the horizontal Bridgman (HB) or floating zone (FZ) technique have been annealed in the range 4~30-80OOC, us,~ally for periods of 16 hr in either the presence or absence of copper. Measurements of thermally stimulated currents, dark conductivity, density, and thermal conductivity were carried out on samples at various stages of annealing. It was found that very large concentrations of traps (>lO19 cm-3) can be introduced by annealing, and these are identified as lattice defects. It is proposed that there are two defects, a donor and an acceptor which occur both paired and isolated in the lattice. When paired, their ionization energies are roughly 0.2 eV, and x~hen isolated are roughly 0.5 eV. There is a fundamental difference between FZ and HB crystals in annealing characteristics and of greatest significance, at 700oc in the absence of copper, the concentration of defects increases in FZ samples and decreases in HB samples. This indicates that the defects are not present in therm~3 equilibrium. Instead, the defects are probably introduced by an accident of growth during the growth process, in a neutral form such as a precipitate or antiphase domain. Copper acts as a catalyst in enhancing the rate of defect annealing. (Received 6 September 1963)
*Operated ~clth support from the U.S. Army, Navy and Air Force.