Semiconductor Side Research Articles

Polaron and bipolaron states in Si-inversion layers: Possible origins and effects

Abstract We report results of a series of multiband tight-binding cluster calculations we have made to further uncover the origin and nature of the intrinsic interface states at the Si-SiO 2 interface as well as their effects on the n- and p-channel inversion layers. These results show that distortion (reconstruction) effects are important ingredients in the description of these states and this together with additional analysis indicates that threefold coordinated Si atoms at the Si-SiO 2 interface as well as strained Si-Si bonds on the oxide “side” on the interface can exist, as we have suggested earlier, in metastable configurations leading to e.g., device instabilities. A subgroup of these reconstructing interface states associated with weakly strained Si-Si bonds on the semiconductor side of the interface is identified and analyzed with emphasis on how such states can give rise to polaronic and bipolaronic effects in inversion layers and hence provide an additional basis for the Anderson-like negative U models previously employed by us in studying the low carrier density regime of this system.

Polaron and bipolaron states in Si-inversion layers: Possible origins and effects

We report results of a series of multiband tight-binding cluster calculations we have made to further uncover the origin and nature of the intrinsic interface states at the Si-SiO 2 interface as well as their effects on the n- and p-channel inversion layers. These results show that distortion (reconstruction) effects are important ingredients in the description of these states and this together with additional analysis indicates that threefold coordinated Si atoms at the Si-SiO 2 interface as well as strained Si-Si bonds on the oxide “side” on the interface can exist, as we have suggested earlier, in metastable configurations leading to e.g., device instabilities. A subgroup of these reconstructing interface states associated with weakly strained Si-Si bonds on the semiconductor side of the interface is identified and analyzed with emphasis on how such states can give rise to polaronic and bipolaronic effects in inversion layers and hence provide an additional basis for the Anderson-like negative U models previously employed by us in studying the low carrier density regime of this system.

General properties of SnO2-GaAs and SnO2-Ge heterojunction photovoltaic cells

SnO 2 -Ge and SnO 2 -GaAs heterojunction formed by chemical vapor deposition have been investigated. The results show that (n-n) SnO 2 -GaAs, (n-p) SnO 2 -GaAs, and (n-n) SnO 2 -Ge heterojunctions give a photovoltaic effect, while (n-p) SnO 2 -Ge yields an ohmic contact. The measured short-circuit currents, arising mainly from semiconductor side, are comparable with those for AMOS and homojunction solar cells. The open-circuit voltage and fill factor and considerably less. The polarity observed in V oc and I sc is consistent with the band bending of a simple SnO 2 -semiconductor heterojunction energy-band diagram neglecting interface states. The ohmic behavior for (n-p) SnO 2 -Ge is attributed to the accumulation layer existing between SnO 2 conduction band and Ge valence band at the interface.

Interface exciton modes and superconducting transition temperature of a metal in contact with a semiconductor

The problem of superconductivity in a metal-semiconductor system has been studied, using the dielectric formulation of superconductivity. The charge redistribution due to the quantum penetration of the metallic electrons to the semi-conductor side is approximated by a simple exponential function. The interface exciton modes are obtained within the framework of classical electrostatics, and their effect in modifying the effective electron-electron interaction near the interface is investigated. It is found that the strength of the excitonic term is small, and by itself, insufficient to lead to superconductivity. Nevertheless, it can alter the superconducting transition temperature of a metal, if it is already superconducting due to some other mechanism. This has been studied as a function of the various parameters entering in the problem.

Characteristics of Waveguides with a Semiconductor Side Wall

The attenuation, guide wavelength, and characteristic impedance of rectangular waveguides with one high conductivity semiconductor side wall have been derived for the case of propagating TE/sub NO/ modes. These properties can be interpreted in terms of the penetration of the microwave electric field into the semiconductor material by an amount of the same order as, but generally unequal to, the classical skin depth. These theoretical results are evaluated for the special case of an indium antimonide side wall in RG 138/U waveguide operating at 110 Gc/s. The calculated attenuation lengths and guide wavelengths for this case are of such magnitude that they can be measured with reasonable accuracy, thus illustrating the value of this technique for the measurement of the electrical properties of semiconductor materials at the higher microwave frequencies.