A PHOTOLUMINESCENCE STUDY OF DELTA-DOPED GAAS

Samples of GaAs delta-doped with beryllium have been studied with phot oluminescence. With a lightly doped sample, (2 x 10(16) Be atoms per m 2) a spectral feature is observed which can be interpreted as caused b y radiative recombinations between spatially non-confined conduction-b and electrons and acceptor-related holes forming a miniband system con fined spatially to the delta-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 wh ich during growth have diffused away from the delta-layer is so high t hat such acceptors drain the photoexcited electrons. A narrow, exciton ic line situated 0.6 meV above the n = 1 free exciton line, lower pola riton branch, is seen, but the well-known defect-induced bound exciton s in the 1504-1512 meV region are not observed. The results are discus sed.