Regensburg 2007 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 9: Semiconductor Laser II

HL 9.4: Talk

Monday, March 26, 2007, 15:30–15:45, H13

Coulomb effects on luminescence spectra and radiative recombination times — •Walter Hoyer, Mackillo Kira, and Stephan W. Koch — Department of Physics and Material Sciences Center, Philipps-University, Renthof 5, 35032 Marburg, Germany

Semiconductor laser structures are of great technological importance while they also offer a unique possibility to study fundamental properties of light-matter interaction. Typically, lasers operate at room temperature or above such that appreciable phonon scattering has to be considered for a realistic description. At the same time, phase-space filling and Coulomb effects such as screening or Auger recombination are important for laser systems, and strong internal electric fields can furthermore complicate the analysis.

Here, a microscopic theory based on Bloch electrons and holes in a two-band approximation is applied in order to compute absorption and luminescence spectra for GaAs-type quantum wells at room temperature. Special focus is set to investigate the effect of Coulomb interaction on the linewidth of the luminescence spectra and on the radiative recombination rates. Since spontaneous emission provides an unavoidable loss mechanism, precise knowledge is important in order to correctly predict laser threshhold densities. Density dependent recombination rates are computed and contrasted with the common assumption of a quadratic increase with density. It is found that even for densities clearly beyond the transparency point a free-carrier model is insufficient for a correct estimate of the radiative recombination rates.