Neutralization of the effect of surface doping at a metal-semiconductor contact

A study is made of the volt-ampere and volt-faraday characteristics of metal-semiconductor contacts formed by the deposition of a number of metals (Al, In, Sn, Cu, Au) onto the surface of a semiconductor (GaAs, Si) subjected to preliminary doping by indium from a molecular beam in a vacuum. It is established that surface doping (SD), while considerably altering the charge and the work function of the free surface of the semiconductor, at the same time has hardly any effect on the properties of the contacts investigated. The deposition of a sublayer of SiO with a thickness of 6–30 Å onto the doped surface before the formation of the contact makes it possible to retain the SD effect even after the application of the contact. The disappearance of the SD effect when the metal is deposited in the absence of a sublayer of SiO is explained by the action of mirror-image forces and the field of the contact potential difference.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 131–134, March, 1977.     

Influence of the Asymmetry of Static Loads on the Vibration Characteristics of Planetary Gearings

A model of planetary double-reduction gearing is used to study how the asymmetry of dynamical loads affects its vibration characteristics. Design methods for reducing the asymmetry of static loads are shown to be efficient     

Effect of vacuum heat treatment on the surface properties of epitaxial GaAs

We have examined the effect of heating under vacuum on the electronic and structural state of the real surface of epitaxial GaAs films. Vacuum heat treatment reduces the height of the surface potential barrier, increases the surface electron affinity, and raises the density of surface recombination centers and traps. The changes in the electrical and physical properties are due to disorder in the subsurface region, which is apparent in the formation of a block GaAs structure and a polycrystalline Ga₂O₃ layer.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 30–34, March, 1980.     

Long-term changes in the surface potential of CdGeP2 single crystals under illumination

A study is made of the variation in the surface potential V_c of p-type CdGeP₂ single crystals during and after illumination. The sign of V_c corresponds to the increase of the work function of the semiconductor surface under illumination. Together with a sharp variation of V_c, a long-term component is observed whose value increases with the increase of the light intensity and the time of exposure of the specimens to light. Slow changes are explained by the presence on the semiconductor surface of an amorphous film, which impedes the electron exchange of the semiconductor with surface states. A model is proposed and a calculation carried out for the long-term kinetics in the small-signal approximation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 51–54, March, 1976.     

Effect of doping the surface of gallium arsenide with gold on the characteristics of Al-(n+-GaAs) contact

The effect of prior treatment of the surface of n⁺-GaAs single crystals in a solution containing gold ions on the volt-ampere characteristic (VAC) of surface-barrier structures is investigated. It is shown that the VAC can be controlled by varying the exposure of the semiconductor to the solution. The experimental results indicate an increase in the tunnel component of the current in the doped structures and are explained within the framework of a model which takes into account the change in the parameters of the dielectric gap (effective thickness and dielectric constant) and of the surface state density at the metal-semiconductor contact with the introduction of gold microimpurity on the interface.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 80–83, February, 1985.The authors are grateful to L. V. Medvedevaya for assistance in the preparation of the specimens and to V. A. Panteleev for discussion of the results.