TUNNELING SPECTROSCOPY OF THE (110)-SURFACE OF DIRECT-GAP III-V SEMICONDUCTORS

Results of tunneling spectroscopy measurements of the (110) cleaved surface of GaAs, InP, GaSb, InAs, and InSb are presented. These materials form the family of direct-gap III-V binary semiconductors. Spectroscopic measurements are performed in ultrahigh vacuum, using a scanning tunneling microscope (STM). Techniques based on variable tip-sample separation are used to obtain high dynamic range (six orders of magnitude) in the measured current and conductance. Detailed spectra are obtained for all the materials, revealing the conduction- and valence-band edges, onset of the higher lying conduction band at the L point in the Brillouin zone, and various features associated with surface states. The precision and accuracy in determining energetic locations of spectral features are discussed. In particular, limitations in the accuracy due to tip-induced band bending is considered.