TUNNELING SPECTROSCOPY OF A 2DEG IN INAS - EXPERIMENT AND THEORY

The narrow energy gap in InAs allows us to investigate the nonparabolic subband structure of an Yb-oxide-InAs (MOS) inversion layer by measuring the tunneling current I(U) between the inversion layer and the bulk valence band. The period of Landau oscillations of d2I/dU2 is used to determine the subband dispersion E(k parallel-to) and the energy dependent effective mass m*(E) of the subband electrons. The experimental results are compared with self-consistent subband calculations taking into account the nonparabolicity, the magnetic field, and - what is important here - the potential difference between inversion layer and InAs-bulk. Besides an exact numerical solution, we discuss self-consistent, but nevertheless analytical, formulations of both the triangular potential approximation and the variational approach.