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HL: Halbleiterphysik
HL 40: Poster III
HL 40.46: Poster
Friday, March 21, 1997, 11:00–14:00, Z
Magnetoexcitons in coupled InGaAs/GaAs quantum wells — •T. Wang, M. Bayer, T. Gutbrod, F. Kieseling, and A. Forchel — Technische Physik, Universit"at W"urzburg, Am Hubland, D-97074 W"urzburg
We report magneto-photoluminescence studies (B<13T) of the exciton states in coupled In0.045Ga0.955As/GaAs quantum wells (QW) separated by GaAs barriers. The excitonic states in these structures can be controlled by varying either the width of the separating GaAs barriers or the number of QW’s. The QW widths were 7.5 nm in all cases and the heterostructures consisted of 2, 3 and 4 QW’s, respectively. In addition, in each series of coupled QW’s the width of the GaAs barriers was varied (1, 3, 5 or 9 monolayers). We find the following features in the optical spectra: (1) The ground-state exciton binding energy shows a highly nonlinear dependence on the number of QW’s and on the GaAs barrier width which originates from the redistribution of the electron and hole wavefunction by the barriers. (2) The spin splitting varies strongly between the different 1s excitons formed in the coupled QW’s. In addition, the splitting increases with the number of QW’s. (3) Depending on the QW structure we observe a strong mixing of heavy- and light-hole excitons, which causes pronounced anticrossings in the magentic field dispersions of the transition energies.