Photoluminescence and x-ray photoelectron spectroscopy study of S-passivated InGaAs(001)

The influence of sulfur passivation on the surface composition of In_0.53Ga_0.47As(001) was investigated with photoluminescence (PL) and x-ray photoelectron spectroscopy (XPS). Films of In_0.53Ga_0.47As(001), epitaxially grown on InP(100) substrates, were S passivated using a dry electron cyclotron resonance (ECR)-plasma deposition process and were either passivated as-prepared, or exposed to a BCl₃ pre-etch prior to passivation. In the spectral range from 1450 to 1750 nm, S passivation enhances the PL yield by approximately an order of magnitude. XPS shows that S binds both to In and As, although preferably to In, and that oxidation is essentially eliminated by the passivation process. The In-S bonds are more stable upon annealing than are the As-S bonds. Furthermore, the pre-etched+H₂S treatment enhances the PL yield beyond that of the H₂S passivation treatment alone and produces a higher ratio of In-S to As-S bonds at the surface. In a second set of experiments, the influence of the ECR power applied to the sample during passivation was examined. The variation of this processing parameter has little effect on the surface composition.