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Tunnelling current versus voltage characteristics in metalinsulator-metal films
World Abstracts on Microelectronics and Reliability derived in this paper from the basic properties of real MOS structures. Results obtained on the basis of the calculation procedure proposed for determination of the TVS currentvoltage characteristics are shown to be in good agreement with experimented data. The statistics of nearest neighbour impuri~' pair fnrmation in semiconductors. A. CHAT'rERJ~A and J. R. IIAusI~R. Physics (.'hem. Solids. 37, 1031 (1976). The equilibrium concentrations of doubly ionized, singly ionized and neutral, nearest neighbor pairs of donor-donor and acccptor-aeceptor type of impurity pairs have been studied at the temperature of diffusion. In the calculations, :the discrete nature of the host lattice and, the internal energies of the pairs have been taken into account. Further, the effect of degeneracy on pair formations was investigated at high levels of doping densities.
SCF-X~ studies of the electronic structures of C, Si and Ge oxides. J. A. Tossl!Lt,. Physics Chem. Solids. 37, 1043 (1976). SCF-X:t scattered wave cluster MO calculations are presented for the oxyanions CO32 , CO 4 , SiO~-, SiO~.-. SiO6s-, GeO44 and GeO s . A comparison of the calculations with available X-ray spectral data shows good agreement. The MO diagrams for CO3 and CO,~ are found to be quite similar, suggesting that the four coordinate oxyanion is not inherently unstable; therefore a quartz polymorph of CO2 may become stable at high pressure. On the other hand, the valence region width of SiO~is much smaller than that of SiO.~ , thus the three-coordinate Si oxyanion is expected to be highly unstable. For the Ge oxyanions the average valence region width is substantially larger in the six-coordinate than in the four-coordinate form, suggesting a preference for octahedral coordination. These observations indicate that although the valence region width is only one factor affecting the total energy of a system, it is predictive of favored coordination number according to the following principle: a change from a higher to a lower coordination number oxyanion of a given cation, M" , will be favorable if the lower coordinate form has a wider valence region at its equilibrium internuclear distance. Surface states and metal overlayers on the (110) surface of GaAs. J. R. CHELIKO'W'SKY,S. G. LOUIE and MARVIN L. COm!N. Solid-St. Commun. 20, 641 (1976). We have found new surface states related to A1 overlayers on the (110) surface of OaAs. These states play a prominent role in the determination of the electronic structure for metalsemiconductor interfaces. The results are consistent with conjectures of Rowe. Christman and Margaritondo based upon recent experimental results for metal overlayers on semiconductor surfaces. Evidence for mobility domains in (100) silicon inve~ion layers. I. EISELI-, H. Gv:s¢|| and G. DORDA. Solid-St. Commun. 20, 677 (1976). In proof of the existence of domains with different mobilities measurements of Shubnikov de Haas oscillations, piezoresistance, and transverse "Hall" field due to mobility anisotropy are provided. The energy splitting between the ground state subbands of different vallcys has been determined. Amplification of acoustic waves in semiconductors with dominants ionized impurity scattering. S. K. SHARMA, S. P. SINGIt and S. S. SI|ARMA.Solid-St. Electron. 19, 1029 (1976). Using the Bohzmann equation with modified collision term we obtain an expression for the attenuation/amplification coefficient of an acoustic wave in a nondegenerate semiconductor in the presence of a d.c. electric fickl. The ionized impurity scattering has been taken as the sole
25
mechanism of the scattering. A comparison of our results with those obtained by using well known Cohen, Harrison and Harrison model is also made.
Charge transfer in charge-coupled devices in the presence of interface states. R. M. BARSAN. Solid-St. Electron. 19, 1015 (1976). The transfer of charge from under a gate of a three-phase surface-channel charge-coupled device is analysed in terms of thermal diffusion, charge-gradient induced drift, fringing field drift, and interface state trapping. A method based on a piecewise approximation for the emission rate from interface statc~ is proposed and used to derive the single-transfer characteristics in the presence of interface traps. It is shown that the emission rate exhibits a marked spatial dependence, which is a function of both fringing field profile and interface state density. It is also concluded that trapping effects are a strong limitation on the transfer cfficiencies attainable in surfacechannel charge-coupled devices at low and moderate frequencies. Anomalous frequency dependence of conductivity of amorphons semiconductor films. K. L. NARASL~tH:X-~t,S. GutI^ and S. C. AGARWAL. Solid-St. Commun 20, 573 (1976). ]'he a.c. conductivity of a-Ge and a-lnSb films is found to obey a e : law with 0.4 < s < 1. s is found to be temperature dependent and its value goes down as the temperature is lowered. The observed temperature dependence of.s cannot be explained by the existing theories for a.c. conduction in amorphous materials. Schnttky solar cells on thin epitaxial silicon. W. A. ANDkRSON, S. M. VERNON, P. M..x]Hr and B. LALEVIC. Solid-St. Electron. 19, 973 (1976). Schottky solar cells fabricated on 10, 20 and 301~m cpitaxial silicon produce a current density ranging from about 10 22 mA/cm 2, depending on Si thickness and orientation, in close agreement with theoretically predicted data. These results are also in close agreement with recent data on p-n solar cells, using thin epitaxial silicon. Data reported herein predict that 10~, efficient Schottky solar cells could be produced using about 20l~ of silicon on a suitable substrate. A 7.6% efficient Schottky solar cell on epitaxial silicon has been recently fabricated and tested using AMI sunlight (100 mW/cm2). Tunnelling current versus voltage characteristics in metalinsulator-metal films. P. KERKU)VS and A. MODINOS. Solid-St. Electron. 19, 1009 (1976). The tunnelling current j(V) and the logarithmic conductivity a(V) _=_(l:j)(dj/dV) are calculated for exactly solvable one-dimensional models of metal-insultator-metal structures. When the tunnelling probability is calculated by the MWKB method, the logarithmic conductivity exhibits a single peak at a value of the applied voltage equal to the barrier height. When the tunnelling probability is calculated this peak is shifted to a higher value of the applied voltage and additional peaks appear at even higher values of the applied voltage, depending on the thickness of the insulating film. This additional structure in a(V) is due to "resonances" in the tunnelling probability which may or may not survive in a three dimensional calculation. A technique for measuring the imlmrity concentration of silicon-on-sapphire flints using C-V plots. EUC,~:NI! R. V~,7ORI.EY. Solid-St. Electron. 19, 997u (1976). The problem of calculating the impurity concentration of lightly doped silicon-onsapphire (SOS) films using a C-V curve is addressed. The existing techniques for calculating impurity concentration and their limitations are briefly discussed. One of these limitations is the low Q of lightly doped SOS capacitors. A technique based on the inflection point slope (maximum
SCF-X~ studies of the electronic structures of C, Si and Ge oxides. J. A. Tossl!Lt,. Physics Chem. Solids. 37, 1043 (1976). SCF-X:t scattered wave cluster MO calculations are presented for the oxyanions CO32 , CO 4 , SiO~-, SiO~.-. SiO6s-, GeO44 and GeO s . A comparison of the calculations with available X-ray spectral data shows good agreement. The MO diagrams for CO3 and CO,~ are found to be quite similar, suggesting that the four coordinate oxyanion is not inherently unstable; therefore a quartz polymorph of CO2 may become stable at high pressure. On the other hand, the valence region width of SiO~is much smaller than that of SiO.~ , thus the three-coordinate Si oxyanion is expected to be highly unstable. For the Ge oxyanions the average valence region width is substantially larger in the six-coordinate than in the four-coordinate form, suggesting a preference for octahedral coordination. These observations indicate that although the valence region width is only one factor affecting the total energy of a system, it is predictive of favored coordination number according to the following principle: a change from a higher to a lower coordination number oxyanion of a given cation, M" , will be favorable if the lower coordinate form has a wider valence region at its equilibrium internuclear distance. Surface states and metal overlayers on the (110) surface of GaAs. J. R. CHELIKO'W'SKY,S. G. LOUIE and MARVIN L. COm!N. Solid-St. Commun. 20, 641 (1976). We have found new surface states related to A1 overlayers on the (110) surface of OaAs. These states play a prominent role in the determination of the electronic structure for metalsemiconductor interfaces. The results are consistent with conjectures of Rowe. Christman and Margaritondo based upon recent experimental results for metal overlayers on semiconductor surfaces. Evidence for mobility domains in (100) silicon inve~ion layers. I. EISELI-, H. Gv:s¢|| and G. DORDA. Solid-St. Commun. 20, 677 (1976). In proof of the existence of domains with different mobilities measurements of Shubnikov de Haas oscillations, piezoresistance, and transverse "Hall" field due to mobility anisotropy are provided. The energy splitting between the ground state subbands of different vallcys has been determined. Amplification of acoustic waves in semiconductors with dominants ionized impurity scattering. S. K. SHARMA, S. P. SINGIt and S. S. SI|ARMA.Solid-St. Electron. 19, 1029 (1976). Using the Bohzmann equation with modified collision term we obtain an expression for the attenuation/amplification coefficient of an acoustic wave in a nondegenerate semiconductor in the presence of a d.c. electric fickl. The ionized impurity scattering has been taken as the sole
25
mechanism of the scattering. A comparison of our results with those obtained by using well known Cohen, Harrison and Harrison model is also made.
Charge transfer in charge-coupled devices in the presence of interface states. R. M. BARSAN. Solid-St. Electron. 19, 1015 (1976). The transfer of charge from under a gate of a three-phase surface-channel charge-coupled device is analysed in terms of thermal diffusion, charge-gradient induced drift, fringing field drift, and interface state trapping. A method based on a piecewise approximation for the emission rate from interface statc~ is proposed and used to derive the single-transfer characteristics in the presence of interface traps. It is shown that the emission rate exhibits a marked spatial dependence, which is a function of both fringing field profile and interface state density. It is also concluded that trapping effects are a strong limitation on the transfer cfficiencies attainable in surfacechannel charge-coupled devices at low and moderate frequencies. Anomalous frequency dependence of conductivity of amorphons semiconductor films. K. L. NARASL~tH:X-~t,S. GutI^ and S. C. AGARWAL. Solid-St. Commun 20, 573 (1976). ]'he a.c. conductivity of a-Ge and a-lnSb films is found to obey a e : law with 0.4 < s < 1. s is found to be temperature dependent and its value goes down as the temperature is lowered. The observed temperature dependence of.s cannot be explained by the existing theories for a.c. conduction in amorphous materials. Schnttky solar cells on thin epitaxial silicon. W. A. ANDkRSON, S. M. VERNON, P. M..x]Hr and B. LALEVIC. Solid-St. Electron. 19, 973 (1976). Schottky solar cells fabricated on 10, 20 and 301~m cpitaxial silicon produce a current density ranging from about 10 22 mA/cm 2, depending on Si thickness and orientation, in close agreement with theoretically predicted data. These results are also in close agreement with recent data on p-n solar cells, using thin epitaxial silicon. Data reported herein predict that 10~, efficient Schottky solar cells could be produced using about 20l~ of silicon on a suitable substrate. A 7.6% efficient Schottky solar cell on epitaxial silicon has been recently fabricated and tested using AMI sunlight (100 mW/cm2). Tunnelling current versus voltage characteristics in metalinsulator-metal films. P. KERKU)VS and A. MODINOS. Solid-St. Electron. 19, 1009 (1976). The tunnelling current j(V) and the logarithmic conductivity a(V) _=_(l:j)(dj/dV) are calculated for exactly solvable one-dimensional models of metal-insultator-metal structures. When the tunnelling probability is calculated by the MWKB method, the logarithmic conductivity exhibits a single peak at a value of the applied voltage equal to the barrier height. When the tunnelling probability is calculated this peak is shifted to a higher value of the applied voltage and additional peaks appear at even higher values of the applied voltage, depending on the thickness of the insulating film. This additional structure in a(V) is due to "resonances" in the tunnelling probability which may or may not survive in a three dimensional calculation. A technique for measuring the imlmrity concentration of silicon-on-sapphire flints using C-V plots. EUC,~:NI! R. V~,7ORI.EY. Solid-St. Electron. 19, 997u (1976). The problem of calculating the impurity concentration of lightly doped silicon-onsapphire (SOS) films using a C-V curve is addressed. The existing techniques for calculating impurity concentration and their limitations are briefly discussed. One of these limitations is the low Q of lightly doped SOS capacitors. A technique based on the inflection point slope (maximum