The effect of As2 and As4 molecular beam species on photoluminescence of molecular beam epitaxially grown GaAs

The first observation of several sharp photoluminescence lines with energies less than the energy of the recombination peak associated with the exciton bound to the neutral carbon acceptor in nominally undoped p-type GaAs grown by molecular beam epitaxy (MBE) is reported. The lines ranging from 1.5110 to 1.5040 eV are interpreted as radiative recombination of defect-induced bound excitons directly correlated with the interaction of As4 molecular beam species during MBE growth. These lines disappear totally when As2 instead of As4 beams are used. We then demonstrate that all sharp photoluminescence features, previously only detected in the best LPE samples, are now also observed in thin MBE GaAs layers when grown from As2 beam species.