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

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.