Scanning tunneling microscopy and spectroscopy study of ultrathin Si interface control layers grown on (001) GaAs for surface passivation

Microscopic topological and spectroscopic properties of the ultrathin silic on interface control layer (Si-ICL) grown by molecular beam epitaxy on the (001) GaAs surface were investigated by the ultrahigh vacuum (UHV), scannin g tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) tech niques, and the results were correlated with the macroscopic electronic pro perties measured by in situ X-ray photoelectron spectroscopy (XPS) and UHV photoluminescence (PL) techniques. Growth of the Si-ICL on c(4 x 4) GaAs su rface produced much more ordered STM topology, leading to better electronic properties as observed by XPS, PL and STS methods than the growth on (2 x 4) surface. In addition to normal STS spectra showing GaAs energy gap, many anomalous spectra showing much wider apparent gaps were observed on all th e surfaces, and they were interpreted to correspond to the pinning centers for the Fermi level where surface states exchange electronic charge with th e STM tip and modify the band bending. (C) 2000 Elsevier Science B.V. All r ights reserved.