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 lo w-temperature buffer have a significant effect on the structure, micro structure, defects and opto-electronic properties of the grown GaN fil ms. The electron mobility in Si-doped GaN films was found to be contro lled both by the density of ionized impurities and the density of disl ocations. 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 x 10(18) cm(-3), but relatively low hole mobilities (0.3 cm(2)/V s). These low mobilities can be impro ved by thermal annealing, a result attributed to the removal of static disorder. (C) 1998 Elsevier Science B.V. All rights reserved.