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Net negative charge of electron-hole drops in germanium
556
World Abstracts on Microelectronics and Reliability
Surface state excitans in semioanducturs. R. DE SOL and E. TOSATTI. Solid St. Commun. 22, 307 (1977). We calculate binding energies and wave-functions of surface state excitons. Our approach is based on the effective mass approximation, and assumes a small but finite surface state penetration depth. Central cell corrections are included. We obtain binding energies in the tenth of eV range, in agreement with recent observations on GaAs (110) and Si (111) 7 × 7, for surface masses of order unity. Effect of heat treatment on chemical and electronic structure of solid SiO; an electron spectroscopy study. G. HOLLINGER, Y. JUGNET and TRAN MINH DUC. Solid St. Commun. 22, 277 (1977). Photoelectron spectroscopy (XPS and UPS) and X-ray excited Auger electron spectroscopy (XAES) measurements for commercial SiO powder and for SiO thin films show direct evidence for the evolution of the chemical structure of SiO from a characteristic metastable phase to a microscopic mixture of Si and SiO2 when the temperature increases. Charge pumping effect and its application in the MOS transistors investigations. ARTUR OWCZAREK and JERZY F. KOLODZIEISKL Electron. Technol. 10, (1) 55 (1977). The theory of charge pumping effect in MOS transistors is presented. The results of pumping current measurements prior to and after the BT test and after the controlled breakdown of metallurgical junctions are given. The possibilities of applying the charge pumping effect to determining the surface states density on the Si-SiO 2 interface are analysed. Properties of a giant electron-hole drop in germanium. J. C. V. MATTOS, J. M. WORLOCK and T. C. DAMEN. Solid St. Commun. 22, 13 (1977). We have observed a giant electron-hole drop in an inhomogeneously stressed germanium crystal. Our measurements show that it is a single giant drop of constant liquid density rather than a cloud of smaller droplets. It has a density of 2 × 10 ~7 electron-hole pairs/cm 3 with a lifetime of only 30 #sec. These results are discussed in the context of earlier reports giving lower densities and longer lifetimes. Relaxation of (111) silicon surface atoms from studies of Si4H9 clusters. A. REDONDO, W. A. GODDARD III, T. C. McGILL and G. T. SURRATT. Solid St. Commun. 21, 991 (1977). Self-consistent Hartree-Fock and generalized valence bond calculations have been performed on clusters modeling the (l ll) silicon surface. We find that the surface state is accurately described as a dangling bond surface orbital with 93% p character. We determined the optimum relaxation of the surface layer to be 0.08 A toward the second layer. In the positive ion, the surface atom relaxes toward the second layer by an additional 0.30A, and for the negative ion the surface atom moves toward the vacuum 0.25 A. The vertical ionization potential was found to be 5.78 eV (experimental values are 5.6-5.9 eV) while the calculated adiabatic electron affinity is 3.02 eV. Sound velocity in amorphous Ge and Si. L. R. TES'rARDI and J. J. HAUSER. Solid St. Commun. 21, 1039 0977). The low frequency velocity of sound for a Young's modulus mode in sputtered amorphous films of Ge and Si is found to be only ~ 55-60% of the value expected for the crystalline state. The reduction is one of the largest associated with crystalline-amorphous polymorphs. A mathematical study of space-charge layer capacitance for an abrupt p - n semiconductor junction. D. P. KENNEDY. Solid-St. Electron. 20, 311 (1977). Simple approximation equations are presented for the space-charge layer capacitance of an abrupt p-n semiconductor junction. By direct comparison with exact capacitance calculations, this approximation method is shown to yield a maximum error of about 3.5% throughout a wide range of impurity atom density and reverse biasing voltage. In addition, calcula-
tions are presented to show the magnitude of error associated with several approximation equations presently available in the technical literature, Measurements of low-frequency noise and surface state concentration in MOS transistors. ARTUR OWCZAREK. Eh'ctron. Technol. 9, (3/4) 43 (1976). The traps density estimation method for the oxide based on the pomping current measurement and on performance of the CMos (l,'~l~) characteristics is described. The results of the low-frequency noise figure measurements of PMOS transistors operating in the nonsaturated region arc presented. The l / f noise dependence on traps density in the oxide is discussed. It is noted that the low-frequency noise level is not affected by the density of "fast" surface states. Pulse measurements of channel conductance in MOS transisturs. ROMAN GARY and JERZY F. KOLODZIEJSK1. Electron, Technol. 9, (3/4) 61 0976). The p-type enhancement channel transistors were investigated. Three methods were applied to determine surface state density. To induce controlled changes of charge distribution at the interface all transistors were subjected to the thermal treatment (BT test). To collect additional data the measurements of selected electrical parameters of transistors have been performed. The paper contains a description of the measurement methods and the measuring systems used, the results of investigations and the attempts to interpret them. Net negative charge of electronq~ole drops in germanium. AARO NAKAMURA. Solid St. Commun, 21, 1111 (1977). The giant fluctuating photocurrent has been observed in highly excited germanium samples with ohmic contacts at 1.6 K. From the observation of this fluctuating photocurrent spike with varying static electric field, it is found that the electron-hole drop is negatively charged as a whole. Diffusivity of charged carriers in semiconductors in strong electric fields, V. V. PARANJAPE. Y. Phys. Chem. Solids 38, 375 (1977). Expressions for diffusivity parallel (Djj) and perpendicular (Dj) to an external electric field in semiconductors are derived by assuming a drifted Maxwellian distribution for the carriers. It is shown that the expressions lbr diffusivity as obtained by Robson are unchanged for arbitrarily large values of the drift velocity- a result which is not expected in his work. Conductivity of complementary error function n-type diffused layers in gallium arsenide. B. JAYAYT BAL~GA, Solid-St. Electron. 20, 321 (1977). The average conductivity of n-type erfc diffused layers in Gallium Arsenide have been calculated for background doping levels of 10~Scm -3. 1 0 ~ c m - 3 and 10~Vcm-3, The curves arc confined to surface concentrations below 10t~ c m 3 because of the strong dependence of diffusion coefficient upon concentration at higher concentrations, Sheet resistivity for planar process control. DENIS L. HElD'IMANN and ROBERT C. THOMAS. Solid St. Technol. p. 43 (February 1977). A modification of the procedure for the measurement of sheet resistivity of a layer diffused into a control slice of opposite conductivity type is described. Instead of a uniform diffusion into a large area slice or into rectangular chips, diffusing a standard bar pattern onto the slice is proposed. This allows a better utilization of the slice, gives information for statistical and for gradient measurements and has possibilities for extensions to the study of base and emitter sheet resistivities (and hs~} in bipolar transistors. Optically induced electron spin resonance in doped amorl~m~ silicon. J. C. KNIGHTS and D. K. BIGELSEN. Solid St. Commun. 22, 133 0977). We report the first observations of optically induced electron spin resonance signals
World Abstracts on Microelectronics and Reliability
Surface state excitans in semioanducturs. R. DE SOL and E. TOSATTI. Solid St. Commun. 22, 307 (1977). We calculate binding energies and wave-functions of surface state excitons. Our approach is based on the effective mass approximation, and assumes a small but finite surface state penetration depth. Central cell corrections are included. We obtain binding energies in the tenth of eV range, in agreement with recent observations on GaAs (110) and Si (111) 7 × 7, for surface masses of order unity. Effect of heat treatment on chemical and electronic structure of solid SiO; an electron spectroscopy study. G. HOLLINGER, Y. JUGNET and TRAN MINH DUC. Solid St. Commun. 22, 277 (1977). Photoelectron spectroscopy (XPS and UPS) and X-ray excited Auger electron spectroscopy (XAES) measurements for commercial SiO powder and for SiO thin films show direct evidence for the evolution of the chemical structure of SiO from a characteristic metastable phase to a microscopic mixture of Si and SiO2 when the temperature increases. Charge pumping effect and its application in the MOS transistors investigations. ARTUR OWCZAREK and JERZY F. KOLODZIEISKL Electron. Technol. 10, (1) 55 (1977). The theory of charge pumping effect in MOS transistors is presented. The results of pumping current measurements prior to and after the BT test and after the controlled breakdown of metallurgical junctions are given. The possibilities of applying the charge pumping effect to determining the surface states density on the Si-SiO 2 interface are analysed. Properties of a giant electron-hole drop in germanium. J. C. V. MATTOS, J. M. WORLOCK and T. C. DAMEN. Solid St. Commun. 22, 13 (1977). We have observed a giant electron-hole drop in an inhomogeneously stressed germanium crystal. Our measurements show that it is a single giant drop of constant liquid density rather than a cloud of smaller droplets. It has a density of 2 × 10 ~7 electron-hole pairs/cm 3 with a lifetime of only 30 #sec. These results are discussed in the context of earlier reports giving lower densities and longer lifetimes. Relaxation of (111) silicon surface atoms from studies of Si4H9 clusters. A. REDONDO, W. A. GODDARD III, T. C. McGILL and G. T. SURRATT. Solid St. Commun. 21, 991 (1977). Self-consistent Hartree-Fock and generalized valence bond calculations have been performed on clusters modeling the (l ll) silicon surface. We find that the surface state is accurately described as a dangling bond surface orbital with 93% p character. We determined the optimum relaxation of the surface layer to be 0.08 A toward the second layer. In the positive ion, the surface atom relaxes toward the second layer by an additional 0.30A, and for the negative ion the surface atom moves toward the vacuum 0.25 A. The vertical ionization potential was found to be 5.78 eV (experimental values are 5.6-5.9 eV) while the calculated adiabatic electron affinity is 3.02 eV. Sound velocity in amorphous Ge and Si. L. R. TES'rARDI and J. J. HAUSER. Solid St. Commun. 21, 1039 0977). The low frequency velocity of sound for a Young's modulus mode in sputtered amorphous films of Ge and Si is found to be only ~ 55-60% of the value expected for the crystalline state. The reduction is one of the largest associated with crystalline-amorphous polymorphs. A mathematical study of space-charge layer capacitance for an abrupt p - n semiconductor junction. D. P. KENNEDY. Solid-St. Electron. 20, 311 (1977). Simple approximation equations are presented for the space-charge layer capacitance of an abrupt p-n semiconductor junction. By direct comparison with exact capacitance calculations, this approximation method is shown to yield a maximum error of about 3.5% throughout a wide range of impurity atom density and reverse biasing voltage. In addition, calcula-
tions are presented to show the magnitude of error associated with several approximation equations presently available in the technical literature, Measurements of low-frequency noise and surface state concentration in MOS transistors. ARTUR OWCZAREK. Eh'ctron. Technol. 9, (3/4) 43 (1976). The traps density estimation method for the oxide based on the pomping current measurement and on performance of the CMos (l,'~l~) characteristics is described. The results of the low-frequency noise figure measurements of PMOS transistors operating in the nonsaturated region arc presented. The l / f noise dependence on traps density in the oxide is discussed. It is noted that the low-frequency noise level is not affected by the density of "fast" surface states. Pulse measurements of channel conductance in MOS transisturs. ROMAN GARY and JERZY F. KOLODZIEJSK1. Electron, Technol. 9, (3/4) 61 0976). The p-type enhancement channel transistors were investigated. Three methods were applied to determine surface state density. To induce controlled changes of charge distribution at the interface all transistors were subjected to the thermal treatment (BT test). To collect additional data the measurements of selected electrical parameters of transistors have been performed. The paper contains a description of the measurement methods and the measuring systems used, the results of investigations and the attempts to interpret them. Net negative charge of electronq~ole drops in germanium. AARO NAKAMURA. Solid St. Commun, 21, 1111 (1977). The giant fluctuating photocurrent has been observed in highly excited germanium samples with ohmic contacts at 1.6 K. From the observation of this fluctuating photocurrent spike with varying static electric field, it is found that the electron-hole drop is negatively charged as a whole. Diffusivity of charged carriers in semiconductors in strong electric fields, V. V. PARANJAPE. Y. Phys. Chem. Solids 38, 375 (1977). Expressions for diffusivity parallel (Djj) and perpendicular (Dj) to an external electric field in semiconductors are derived by assuming a drifted Maxwellian distribution for the carriers. It is shown that the expressions lbr diffusivity as obtained by Robson are unchanged for arbitrarily large values of the drift velocity- a result which is not expected in his work. Conductivity of complementary error function n-type diffused layers in gallium arsenide. B. JAYAYT BAL~GA, Solid-St. Electron. 20, 321 (1977). The average conductivity of n-type erfc diffused layers in Gallium Arsenide have been calculated for background doping levels of 10~Scm -3. 1 0 ~ c m - 3 and 10~Vcm-3, The curves arc confined to surface concentrations below 10t~ c m 3 because of the strong dependence of diffusion coefficient upon concentration at higher concentrations, Sheet resistivity for planar process control. DENIS L. HElD'IMANN and ROBERT C. THOMAS. Solid St. Technol. p. 43 (February 1977). A modification of the procedure for the measurement of sheet resistivity of a layer diffused into a control slice of opposite conductivity type is described. Instead of a uniform diffusion into a large area slice or into rectangular chips, diffusing a standard bar pattern onto the slice is proposed. This allows a better utilization of the slice, gives information for statistical and for gradient measurements and has possibilities for extensions to the study of base and emitter sheet resistivities (and hs~} in bipolar transistors. Optically induced electron spin resonance in doped amorl~m~ silicon. J. C. KNIGHTS and D. K. BIGELSEN. Solid St. Commun. 22, 133 0977). We report the first observations of optically induced electron spin resonance signals