PHOTOLUMINESCENCE SPECTROSCOPY OF INTERSUBBAND POPULATION-INVERSION IN A GAAS ALXGA1-XAS TRIPLE-BARRIER TUNNELING STRUCTURE/

We have used interband photoluminescence (PL) spectroscopy to demonstr ate the occurrence of an inter-subband population inversion in a GaAs/ AlxGa1-xAs triple barrier structure containing asymmetric coupled quan tum wells. The relative populations of the n=1 (EI) and n=2 (E2) elect ron subbands of the wider quantum well (QW1) are deduced from the rela tive intensities of the PL peaks arising from recombination of the El and E2 electrons. A significant population inversion is obtained betwe en E2 and EI when the structure is biased so that El is in resonance w ith the n = I (E1) level of the narrower quantum well (QW2). The key importance of the interwell resonance in achieving population inversio n is confirmed by comparison with PL results from structures in which E1-E1 alignment does not occur.