Silicon incorporation behaviour in GaAs grown on GaAs (111)A by molecular beam epitaxy

We have made a systematic study of the effect of growth conditions on Si incorporation in GaAs layers grown on GaAs (111)A substrates. We show that it is dominated by the low incorporation coefficient of As-4 on the GaAs (111)A surface. The site occupancy of the Si has been shown by local vibrational mode spectroscopy to be on Ga and As lattice sites to provide donor and acceptor character, respectively. The doping behaviour of Si for specific growth conditions may be predicted from the product of the As-4:Ga flux ratio and the As-4 incorporation coefficient at the growth temperature. The growth conditions for which Si acts as an acceptor produce films with poor surface morphology.