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 silicon interface control layer Si-ICL.grown by molecular beam epitaxy on the 001.GaAs surface were investigated by the ultrahigh vacuum UHV., scanning tunneling microscopy STM.and scanning tunneling spectroscopy STS.techniques, and the results were correlated with the macroscopic electronic properties measured by in situ X-ray photoelectron spectroscopy XPS.and UHV photoluminescence PL.techniques. Growth of the Si-ICL on c 4=4.GaAs surface produced much more ordered STM topology, leading to better electronic properties as observed by XPS, PL and STS methods than the growth on 2=4.surface. In addition to normal STS spectra showing GaAs energy gap, many anomalous spectra showing much wider apparent gaps were observed on all the surfaces, and they were interpreted to correspond to the pinning centers for the Fermi level where surface states exchange electronic charge with the STM tip and modify the band bending. q2000 Elsevier Science B.V. All rights reserved.