PHOTOINDUCED ABSORPTION WITHIN THE VALENCE GAMMA-SUBBAND AND THE CONDUCTION L-SUBBAND MANIFOLDS IN UNDOPED GASB ALSB SUPERLATTICES/

We report the observation of L-valley conduction intersubband absorpti on together with Gamma- valence intersubband in optically excited undo ped, indirect binary-binary short period GaSb/AlSb superlattices. The transitions were identified by comparing their position and polarizati on with calculations which take into account both valence and conducti on subbands. The dependence of the intersubband absorption on the temp erature, excitation intensity and modulation frequency, indicates that the photoexcited carriers are trapped with an activation energy of si milar or equal to 50 mu meV and are long lived (similar or equal to 5 mu sec).