p and n type doping of cubic GaN on SiC(001)

n-type doping with Si and p-type doping with Mg are reported for cubic GaN grown by molecular beam epitaxy (MBE) on cubic SiC(001). Mg incorporation a s high as I x 10(19) cm(-3) has been reached at low growth temperatures. Ho wever, no correlation is found between the hole concentration and Mg concen tration, probably due to deep levels induced by the stacking faults and the residual doping present in the layer, as revealed by the deep optical tran sition which dominates the photoluminescence (PL) spectra. In contrast, n-t ype doped samples with Si are much better controlled, with a maximum value of 5 x 10(19) cm(-3) for the free electron concentration, and with a clear donor signature in their PL spectra. (C) 2001 Elsevier Science B.V. All rig hts reserved.