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.