Dresden 2006 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 15: III-V semiconductors II

HL 15.5: Vortrag

Dienstag, 28. März 2006, 12:00–12:15, POT 51

Magneto-excitons in GaInNAs / GaAs quantum well structures — •M. Hetterich, A. Grau, W. Löffler, and H. Kalt — Institut für Angewandte Physik and Center for Functional Nanostructures (CFN), Universität Karlsruhe, D-76131 Karlsruhe, Germany

In recent years, GaInNAs-based quantum wells have attracted considerable interest due to their possible utilization in near-infrared optoelectronic devices. From a band structure point of view, Ga(In)NAs is quite unusual, because the interaction of N-related states with the conduction band leads to a strong non-parabolicity of the latter, which can be described within the so-called band anti-crossing (BAC) model.

In this contribution we investigate the influence of a magnetic field (up to B=14 T) on the excitonic states in GaInNAs / GaAs quantum wells with various compositions and well widths. Magneto-photoluminescence has been used to measure the diamagnetic shift of the exciton ground state. In addition, absorption measurements have been carried out to investigate the field dependence of excited magneto-exciton states. The theoretical approach we use to fit our data is based on the BAC model for the conduction band and a 4-band Luttinger Hamiltonian for the valence bands. The coupling between the valence and conduction bands is taken into account perturbatively using a semi-empirical approach. The in-plane part of the exciton wavefunction is expanded in a Gaussian basis set and the resulting generalized eigenvalue problem is solved numerically on a parallel computer. From a comparison between theory and experiment we can extract data for the exciton binding energy as well as the conduction band dispersion in GaInNAs / GaAs quantum wells.