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HL: Halbleiterphysik
HL 22: Poster II
HL 22.65: Poster
Dienstag, 18. März 1997, 15:30–18:30, Z
Polaritonic and coherence effects in electrooptical spectra of superlattices — •M. Dressler1, F. Bassani1, and G. Czajkowski2 — 1Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy — 2University of Technology and Agriculture, Kaliskiego 7, PL-85-796 Bydgoszcz, Poland
We show how to compute the optical functions (reflectivity, transmittivity, and absorption) for semiconductor superlattices exposed to a uniform electric field in the growth direction including the exciton-polariton effects. The field strength is chosen to be small enough to avoid Wannier-Stark (WS) localization but strong enough to observe Franz-Keldysh oscillations (FKO). The electron-hole screened Coulomb potential is adopted, and the valence band structure is taken into account in the cylindrical approximation. Our approach includes the coherence between the carriers and the electromagnetic field. The lineshapes of all optical functions in the region of anomalous dispersion is then computed with the addition of a phenomenological lifetime broadening. For SL’s of total thicknesses large compared to the exciton Bohr radius we obtain the coexistence of a number of electrooptic modes corresponding to the excitons considered and the radiative mode. The exciton-polaritons show a red shift for small values of the strength of the applied electric field and the FKO in the radiative regions.