Scanning Tunneling Spectroscopy on III–V Materials: Effects of Dimensionality, Magnetic Field, and Magnetic Impurities

Abstract

We review low-temperature scanning tunneling spectroscopy (STS) investigations of the local electron density of states (LDOS) of different electron and hole systems in III–V semiconductors. By cleavage of InAs or InSb, a clean (110) surface can be prepared, with no intrinsic surface states in a range of ± 1 eV around the band edges, which is the relevant energy window for STS. This allows the study of the electronic properties of the simple parabolic, s-like conduction band, thus giving access to effects induced by interaction. Systems in different dimensions and in an applied magnetic field have been studied in real space on the atomic scale in order to disentangle the interesting but complex interaction of electrons with disorder. We focus on a comparison between the three-dimensional (3D) electron system and the two-dimensional (2D) electron system with and without magnetic fields. While without a magnetic field, the electronic wave functions are much more complex in 2D than in 3D, an appealing similarity has been found in high magnetic fields. In 2D, the imaged states can be clearly identified with the states responsible for integer quantum Hall transitions. The origin of the 3D states appearing in the extreme quantum limit is still not clear. Furthermore, by doping the semiconductor with magnetic acceptors like Mn, the properties of the bound hole and its interaction with the tip-induced potential can be studied on the local scale. The LDOS of the hole has a strongly anisotropic shape, which is further disturbed by interaction with the (110) surface.