Surface treatments of SiGe for scanning tunneling microscopy/spectroscopy and characterization of SiGe p-n junction

Abstract

Hydrogen-termination of SiGe(001) surfaces for scanning tunneling microscopy/spectroscopy (STM/STS) measurements was realized by optimizing the chemical treatment. It was found that the chemical oxidation with H2SO4 made the SiO2∕SiGe interface smooth and that the resultant hydrogen-terminated surface treated in the HF+HCl solution had few surface states in the band gap. This surface enabled the authors to evaluate the electrical properties of SiGe by STM/STS. Using the chemical method developed here, STM images of SiGe p-n junctions clearly visualized the existence of the depletion region. Furthermore, the distribution of the local electric properties of SiGe p-n junctions could be revealed with the spatial resolution better than 5×5nm2. It is concluded that STM/STS is a powerful technique to evaluate the local properties of Si∕SiGe devices.