ABSTRACT
It is widely known that surface treatments, by chemical liquids and/or plasmas, give influences to density and distribution of surface states and electrical characteristics of compound semiconductor devices, especially in those that utilize surface/interface phenomena such as Schottky gates or metal-insulator-semiconductor (MIS) gates. Tsuzuku et al demonstrated that surface oxygen density at the surface of GaAs is affected by pH value of the treatment chemicals and NH4OH treated surface has less oxygen but higher density of interface states when a Schottky junction is formed [1] as compared with those of HC1 treated wafers. Hara et al demonstrated improvement of a MIS junction by nitrogen plasma treatment[2]. Also many experimental activities to reduce the densities of the surface/interface states by covering the top surfaces with sulphur[3], silicon [41, [5] etc, and identification of failure mechanisms have been reported, which are related with combinations of chalcogen atoms and group V elements [6], [7]
Microscopic theoretical studies about semiconductor surfaces and influences of adsorption of foreign elements on the surfaces have also been reported recently. Ohno reported first-principles studies of a sulphur-passivated GaAs (100)-(1 x 1) surface [8]’ [9]. He determined that S atoms adsorb at bridge sites of the surface, which having been
experimentally identified by Sugiyama et a l [10] later, and explained mechanisms of the passivation. In this paper, we theoretically study electronic states of InP (100)-(1 x 1) surface and influences of chalcogen atoms (in this paper O and S) adsorption to the surface states.
