GAMMA GAMMA PHOTOLUMINESCENCE FROM TYPE-II SHORT-PERIOD GAAS-ALAS SUPERLATTICES

Type II short-period (GaAs)n-(AlAs)n superlattices have an indirect band gap with the X conduction band minimum in the AlAs layer and the GAMMA valence band maximum in the GaAs layer. The transfer rate of excited electrons from GAMMA to X is high compared to the direct GAMMA-GAMMA recombination rate, so the indirect X-GAMMA transition predominates in the photoluminescence spectra. The GAMMA-GAMMA photoluminescence is very weak and has not been reliably reported for n < 7. This paper reports clear GAMMA-GAMMA photoluminescence and its decay for n = 1, 2, 3 and 4 (GaAs)n-(AlAs)n superlattices, and compares the positions to theory as well as to measurements on the GAMMA-GAMMA transition by other techniques.