CONTACTLESS ELECTROMODULATION INVESTIGATIONS OF SURFACE-INTERFACE ELECTRIC-FIELDS IN SEMICONDUCTOR MICROSTRUCTURES

This article reviews some recent experiments using contactless electromodulation techniques, i.e., photoreflectance and contactless electroreflectance, to investigate the surface/interface electric fields in (a) pseudomorphic GaAlAs/InGaAs/GaAs modulation-doped quantum well structures (including the determination of the two-dimensional electron gas density) and (b) Fermi-level pinning on n- and p-type GaAs (001) surfaces. Evidence for the reduced surface state density on p-type material will be presented from both prior and new experiments.