Effect of Annealing and Sulfur Passivation of GaAs Surface in ZnSe/GaAs Heterostructure

We report the effect of annealing and sulfur (S) passivation of GaAs surface on the interface characteristics and interdiffusion problem in ZnSe/GaAs heterostructures whose ZnSe layers are grown by atomic layer epitaxy (ALE) and metalorganic molecular beam epitaxy (MOMBE). The photoluminescence (PL) intensity of self-activated centers created due to interdiffusion at 500°C in the conventionally grown sample is 3-14 times higher than that in the S-passivated sample. Secondary ion mass spectroscopy (SIMS) data suggest that after annealing, Ga and As concentration in the ZnSe epilayer is lower in S-passivated materials. These features suggest that heterostructures are thermally stable in S-passivated material. As a result of S-passivation, full width at half maximum (FWHM) values of X-ray rocking curves are greatly reduced and we could, without postgrowth annealing, achieve well-defined C-V characteristics of a metal/pseudoinsulating ZnSe/GaAs metal-insulator-semiconductor (MIS) diode. Sulfur passivation is an important tool for the fabrication of high-quality heterostructures of II-VI and III-V semiconductors.