RECOMBINATION LIFETIME MEASUREMENTS IN ALGAAS GAAS QUANTUM-WELL STRUCTURES/

We report the results of photoluminescence and minority carrier lifeti me measurements on a set of lightly doped AlGaAs/GaAs quantum well str uctures grown by solid source molecular beam epitaxy. Growth temperatu res 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 radiat ive lifetimes expected for the doping levels used, so we interpret our results in terms of Shockley-Read recombination via deep centres in t he barrier material. Lifetimes measured on n- and p-type samples are c losely similar, which can be explained in terms of a modified version of the standard Shockley-Read process, appropriate to the pseudo two-d imensional structures of interest here, provided the recombination cen tre is acceptor-like. We propose that it is related to oxygen incorpor ated in the Al-containing barrier regions.