Optical study of intersubband transitions in GaSb/AlGaSb systems for QWIPs

The realization of long-wavelength normal-incidence photodetectors relying on interconduction subband absorption in GaSb-based multi-quantum well (MQW) systems has been proven to be possible. High efficiencies can be achieved based on the size-induced Γ-to-L subband crossover in GaSb wells with an electron spill-over from the Γ to the ellipsoidal L conduction subbands. A systematic study of the intersubband absorption in n-GaSb/AlGaSb MQWs as a function of the n-doping and temperature is presented. In particular, medium-infrared transmittance measurements at normal-incidence evidenced sharp bands, corresponding to a peak fractional absorption per well which is higher than that reported in literature on similar systems.