Cross-sectional low-temperature scanning tunneling spectroscopy of an InAs p–n junction

Abstract

Scanning tunneling spectroscopy was used to examine the cross-sectional surface of an InAs p–n junction at low temperature. The depletion layer only in the p-type region was studied by employing a substrate that was doped with large amounts of donor and acceptor impurities as the n-type region. The energy band profile for the p–n junction reveals that the width of the depletion layer in the n-type region is negligibly small. Compared with the expected width of the depletion layer in the p-type region on the basis of the doped acceptors, the observed width is much wider, indicating the low ionization ratio of the acceptors at low temperature. Owing to the small amount of tip-induced band bending (TIBB) for the conduction band in the p-type region, the observed conduction band edge is fitted well with a simple calculation. In contrast, the observed valence band edge is modified by the TIBB.