We have found that treatment with a solution of ammonium sulfide containing excess sulfur [(NH4) 2Sx] produced a stabilized surface of GaAs. The treated surface is covered with a monomolecular layer of sulfur, and oxygen atoms are prohibited from adsorbing chemically on this surface. We checked the durability of the treated surface to heat treatment to find that it was stable up to more than 500 °C. Epitaxial growth of an Al film was demonstrated on the (NH4) 2Sx-treated surface. The presence of sulfur atoms at the interface by this treatment was found to suppress the chemical reaction between the metal and GaAs. Low temperature GaAs epitaxy was demonstrated on the sulfide treated surface without conventional heat treatment. The surface treatment correlates with changes in Schottky barrier height with various metals, which suggests that the surface states of GaAs are decreased remarkably.

The DX center has been studied by Deep Level Transient Spectroscopy in series of GaAs-Ga1-xAlxAs (x = 0.3) and GaAs-AlAs short period superlattices. The existence or not of this center can be understood if its energy level is linked to the L miniband. This suggest a possible way to suppress them by using specific superlattices.

The electron paramagnetic resonance study of the DX center in Sn doped direct gap Ga0.69Al0.31 As shows the existence of a shallow effective mass like excited configuration of this defect. The photoexcitation spectrum for this transformation has a threshold at 0.8 eV; the photoionization of the DX center is not a transition to the lowest r conduction band as previously assumed. After photoexcitation additional paramagnetic defects are observed.

Transient decay of persistent photoconductivity (TDPPC) is employed to assess the donor- or acceptor-like nature of the DX defect in AlGaAs. The TDPPC data is analyzed in terms of the non-equilibrium capture kinetics of DX and a variation in the mobility due to ionized impurity scattering as calculated by the Brooks-Herring equation. TDPPC measurements show DX to be donorlike.

We formulate a consistent defect chemical model of the effect of air/02 anneals on CuInSe2 polycrystalline thin films. The model centers on O-induced neutralization of (near) surface donor states in CuInSe2 grains. The simplest identification of these states is with ionized Se vacancies, due to coordinatively unsaturated In on grain surfaces and boundaries.