INTERSUBBAND L-VALLEY AND HEAVY-HOLE TRANSITIONS IN UNDOPED GASB ALSBSUPERLATTICES/

We report the observation of L-valley-conduction intersubband absorpti on concurrent with Gamma-valence intersubband absorption in optically excited undoped binary-binary short-period GaSb/AlSb superlattices. Un der above-band-gap optical excitation, electrons in these structures o ccupy the lowest-energy L-valley subband, while holes occupy the highe st-energy Gamma subband. Due to the separation in k space, these popul ations have long lifetimes, which enables the observation of photoindu ced intersubband absorption. Due to the symmetry of the L valleys, the ir contribution to the intersubband absorption is observed for bath s- and p-polarized infrared light, in agreement with theoretical predict ions.