Sulfide passivating coatings on GaAs(100) surface under conditions of MBE growth of 〈II–VI〉/GaAs

Abstract

Atomic-force microscopy was applied to compare the topographies of naturally oxidized surfaces of GaAs(100) substrates and those substrates treated with aqueous solutions of sodium sulfide in various stages of their preparation for growth of ZnSe-based heterostructures by molecular beam epitaxy (MBE). It was found that annealing of oxidized substrates strongly disrupts the surface planarity and leads to the appearance of pits with density of 1010 cm−2. The pit density can be reduced by two orders of magnitude by treating the substrate surface with an aqueous solution of Na2S. Transmission electron microscopy demonstrated that sulfidation of GaAs substrates makes it possible to reduce the number of stacking faults at the ZnSe/GaAs interface to ∼3×105 cm−2 and, correspondingly, to improve the structural perfection of MBE-grown II–VI layers and heterostructures.