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Electrical activity of copper in GaAs
314
A B S T R A C T S ON" M I C R O E L E C T R O N I C S A N D R E L I A B I L I T Y
Ge/Si are reported and can be accounted for on the basis of a hetero-junction theory including interface states. The electron affinity difference (×o,-×si) is 0-15 + 0-03 eV as determined from the Ge/Si n - n structures. Alloys for GaAs devices. J. R. DALS and M. J. JOSH, Solid-State Electron., Vol. 7, 1964, pp. I77-181. This paper describes a series of alloys that have been developed for making GaAs devices using alloyed contacts. Conditions affecting wetting properties, penetration depth and type of re-grown layers are discussed. The dependence of the alloying properties on the orientation and preparation of the substrate, with metallographic techniques for assessing these properties, are described. The solubilities and distribution coefficients o f Zn in GaAs and GaP. L. L. CHANG and G. L.
PEA~ON, .y. Phys. Chem. Solids, Vol. 25, 1964, pp. 23-30. The solubilities of zinc in gallium arsenide and gallium phosphide have been measured at temperatures between 700 and l l00°C from constant vapour source diffusion experiments using radioactive Zn 's. The solubilities of neutral impurities in these semiconductors can be calculated from the ionization equilibrium of impurities in the solids. By treating Zn-GaAs and Zn-GaP as binary alloys, assuming ideal liquidus solutions and considering the transfer of neutral species, the solubilities and distribution coefficients have been calculated as a function of temperature up to the melting point of the semiconductors. A sharp increase of the distribution coefficient is predicted for these systems at temperatures approaching the melting point. The intrinsic carrier concentration of GaAs and GaP at the melting point has been found to be higher than that extrapolated from the low temperature value. The relation between solid solubility and zinc vapour pressure at a fixed temperature has been investigated. Theoretical calculations give results in good agreement with the experimental data in the dilute range of zinc. Hot-electron e m i s s i o n from n-silicon. E. A. DAvxEs,J.
Phys. Chem. Solids, Vol. 25, 1964, pp. 201209. Hot-electron emission has been obtained from 70 ~-cm n-Si after treating the emitting surface with caesium to lower the electron affinity. Saturated emission currents rising to a maximum of 2.57 mA/cm °- in fields up to 57 kV/cm were measured. Empirical values of electron temperature have been calculated from the measured emission using the Richardson-Dushman equation and the results compared with electron temperatures calculated from a theoretical formula given by Stratton.
Electrical activity of copper in GaAs. J. BLANCand L. R. WEISBERG,~¢. Phys. Chem. Solids, Vol. 25, 1964, pp. 221-223. It has been established that there is a one-to-one correspondence between the concentration of aeceptors of 0.15 eV ionization energy and the concentration of copper introduced in GaAs between 600 ° and 1000°C. Early data on the solubility of copper in GaAs above 700°C have been confirmed. It has also proved possible to remove copper from GaAs by immersion in molten KCN. Behaviour of lattice defects in GaAs. J. BLANC,R. H. BUBE and L. R. WEXSBERC,J.
Phys. Chem. Solids, Vol. 25, 1964, pp. 225-240. Single crystalline samples of GaAs grown by either the horizontal
Bridgman (HB) or floating zone (FZ) technique have been annealed in the range 450 to 800°C, usually 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 ( > 101' 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 when isolated are roughly 0.5 eV. There is a fundamental difference between FZ and HB crystals in annealing characteristics and of greatest significance, at 700°C 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 thermal 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.
A B S T R A C T S ON" M I C R O E L E C T R O N I C S A N D R E L I A B I L I T Y
Ge/Si are reported and can be accounted for on the basis of a hetero-junction theory including interface states. The electron affinity difference (×o,-×si) is 0-15 + 0-03 eV as determined from the Ge/Si n - n structures. Alloys for GaAs devices. J. R. DALS and M. J. JOSH, Solid-State Electron., Vol. 7, 1964, pp. I77-181. This paper describes a series of alloys that have been developed for making GaAs devices using alloyed contacts. Conditions affecting wetting properties, penetration depth and type of re-grown layers are discussed. The dependence of the alloying properties on the orientation and preparation of the substrate, with metallographic techniques for assessing these properties, are described. The solubilities and distribution coefficients o f Zn in GaAs and GaP. L. L. CHANG and G. L.
PEA~ON, .y. Phys. Chem. Solids, Vol. 25, 1964, pp. 23-30. The solubilities of zinc in gallium arsenide and gallium phosphide have been measured at temperatures between 700 and l l00°C from constant vapour source diffusion experiments using radioactive Zn 's. The solubilities of neutral impurities in these semiconductors can be calculated from the ionization equilibrium of impurities in the solids. By treating Zn-GaAs and Zn-GaP as binary alloys, assuming ideal liquidus solutions and considering the transfer of neutral species, the solubilities and distribution coefficients have been calculated as a function of temperature up to the melting point of the semiconductors. A sharp increase of the distribution coefficient is predicted for these systems at temperatures approaching the melting point. The intrinsic carrier concentration of GaAs and GaP at the melting point has been found to be higher than that extrapolated from the low temperature value. The relation between solid solubility and zinc vapour pressure at a fixed temperature has been investigated. Theoretical calculations give results in good agreement with the experimental data in the dilute range of zinc. Hot-electron e m i s s i o n from n-silicon. E. A. DAvxEs,J.
Phys. Chem. Solids, Vol. 25, 1964, pp. 201209. Hot-electron emission has been obtained from 70 ~-cm n-Si after treating the emitting surface with caesium to lower the electron affinity. Saturated emission currents rising to a maximum of 2.57 mA/cm °- in fields up to 57 kV/cm were measured. Empirical values of electron temperature have been calculated from the measured emission using the Richardson-Dushman equation and the results compared with electron temperatures calculated from a theoretical formula given by Stratton.
Electrical activity of copper in GaAs. J. BLANCand L. R. WEISBERG,~¢. Phys. Chem. Solids, Vol. 25, 1964, pp. 221-223. It has been established that there is a one-to-one correspondence between the concentration of aeceptors of 0.15 eV ionization energy and the concentration of copper introduced in GaAs between 600 ° and 1000°C. Early data on the solubility of copper in GaAs above 700°C have been confirmed. It has also proved possible to remove copper from GaAs by immersion in molten KCN. Behaviour of lattice defects in GaAs. J. BLANC,R. H. BUBE and L. R. WEXSBERC,J.
Phys. Chem. Solids, Vol. 25, 1964, pp. 225-240. Single crystalline samples of GaAs grown by either the horizontal
Bridgman (HB) or floating zone (FZ) technique have been annealed in the range 450 to 800°C, usually 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 ( > 101' 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 when isolated are roughly 0.5 eV. There is a fundamental difference between FZ and HB crystals in annealing characteristics and of greatest significance, at 700°C 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 thermal 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.