Quasi-two-dimensional photoexcited carriers in GaAs doping superlattices

Periodic multilayer structures of GaAs exhibit new semiconductor properties such as tunable effective band gap, long lifetime of photoexcited carriers, and quantization of carriers in space-charge-induced potential wells. We present a more careful treatment of the high excitation regime, where the subbands broaden into minibands, than earlier self-consistent calculations. Experimentally we have used photoluminescence and resonant in-elastic light scattering measurements to study the subband structure. The luminescence peak is found to shift with decreasing photoexcitation intensity far below the band gap of GaAs. By comparing the peak position with the theory we determine the carrier concentration. Resonant spin-flip single-particle excitations directly give the subband splittings which are in good agreement with the theoretical results. At high excitation intensities, the subbands merge and a quasi-three-dimensional behavior is found.