G. Gobsch

Subband structure calculation for inversion layers in InAs and InP

Abstract The complete electronic subband structure of n-inversion layers of InAs- and InP-MIS systems is calculated using a new approximate self-consistent method. Remarkable agreement with recently published experimental results is obtained if the non-parabolicity of the conduction band is taken into account. Landau levels are calculated also for InP accounting for the non-parabolicity.

Theoretical analyses of the Shubnikov-de Haas oscillation in InSb inversion layers

Abstract A calculation is presented of the subband and Landau energy levels in inversion layers adjacent to grain boundaries in InSb bicrystals. Within a rather simplified model the transverse magnetoresistance is calculated and compared with recent experiments. Some unexpected new features in the Shubnikov-de Haas oscillations are related to the occupation of several electric subbands.

Landau levels and SdH-oscillations of the quasi two-dimensional electron gas at grain boundaries and near heterojunctions

Abstract For the quasi two-dimensional (Q2D) electron gas important experimental information is obtained from magnetotransport measurements with a perpendicular magnetic field. The energy spectrum consists of series of Landau levels for each electric subband. There still exist several open questions if two or more electric Subbands are populated. Results are presented here for this situation. The usual procedure for interpreting Shubnikov-de Haas (SdH) measurements for the case of several populated subbands is analyzed (connection with the saw-tooth like Fermi energy as a function of the magnetic field). The transverse magnetoresistance is calculated for the Q2D electron gas in InSb-bicrystals and at InGaAs-InP heterojunctions. All details of the experimental curves can be explained including an anomalous behaviour of the quantum Hall effect (QHE) in the second system. Basic assumptions of the theory are the broadening of the Landau levels and in addition a background of localized states in the second case. The dependence of the electronic structure on the perpendicular magnetic field is discussed qualitatively. First results of magnetic field dependent self-consistent calculations for inversion layers are presented. It is shown for the first time that this magnetic field dependence causes qualitative changes of the Landau level spectrum.