Effects of growth temperature on Mg-doped GaN grown by ammonia molecular beam epitaxy

The hole concentration p in Mg-doped GaN films grown by ammonia molecular beam epitaxy depends strongly on the growth temperature T-GR. At T-GR = 760 degrees C, GaN:Mg films showed a hole concentration of p = 1.2 x 10(18) cm(-3) for [Mg] = 4.5 x 10(19) cm(-3), while at T-GR = 840 degrees C, p = 4.4 x 10(16) cm(-3) for [Mg] = 7 x 10(19) cm(-3). Post-growth annealing did not increase p. The sample grown at 760 degrees C exhibited a low resistivity of 0.7 Omega cm. The mobility for all the samples was around 3-7 cm(2)/Vs. Temperature-dependent Hall measurements and secondary ion mass spectroscopy suggest that the samples grown at T-GR > 760 degrees C are compensated by an intrinsic donor rather than hydrogen. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4751108]