MBE growth and doping of III–V nitrides

We report on the growth and doping of GaN by molecular-beam epitaxy on the c-plane of sapphire. We find that the steps of nitridation and low-temperature buffer have a significant effect on the structure, microstructure, defects and opto-electronic properties of the grown GaN films. The electron mobility in Si-doped GaN films was found to be controlled both by the density of ionized impurities and the density of dislocations. This result is consistent with the model which assumes that dislocations introduce acceptor centers. Films were doped p-type with Mg with carrier concentration up to 6×1018 cm−3, but relatively low hole mobilities (0.3 cm2/V s). These low mobilities can be improved by thermal annealing, a result attributed to the removal of static disorder.