A photoluminescence study of δ-doped GaAs

Samples of GaAs 8-doped with beryllium have been studied with photoluminescence. With a lightly doped sample, (2 x 1016 Be atoms per m2) a spectral feature is observed which can be interpreted as caused by radiative recombinations between spatially non-confined conductionband electrons and acceptor-related holes forming a miniband system confined spatially to the &doped region. With higher densities of Be, this weak feature disappears. Instead, strong recombination to bulk Be acceptors shows up, indicating that the bulk-density of Be atoms which during growth have diffused away from the 6-layer is so high that such acceptors drain the photoexcited electrons. A narrow, excitonic line situated 0.6 meV above the n = 1 free exciton line, lower polariton branch, is seen, but the well-known defect-induced bound excitons in the 1504-1512 meV region are not observed. The results are discussed.