RECOMBINATION LIFETIME MEASUREMENTS IN ALGAAS/GAAS QUANTUM-WELL STRUCTURES

We report the results of photoluminescence and minority carrier lifetime measurements on a set of lightly doped AlGaAs/GaAs quantum well structures grown by solid source molecular beam epitaxy. Growth temperatures were varied between 600 and 700-degrees-C and the arsenic supplied in dimer or tetramer form. The lifetimes show a marked dependence on growth temperature when As4 is used, peaking sharply in the region of 675-degrees-C, but are sensibly independent of growth temperature when using As2. They are nearly an order of magnitude less than the radiative lifetimes expected for the doping levels used, so we interpret our results in terms of Shockley-Read recombination via deep centres in the barrier material. Lifetimes measured on n- and p-type samples are closely similar, which can be explained in terms of a modified version of the standard Shockley-Read process, appropriate to the pseudo two-dimensional structures of interest here, provided the recombination centre is acceptor-like. We propose that it is related to oxygen incorporated in the Al-containing barrier regions.