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

Abstract

The hole concentration p in Mg-doped GaN films grown by ammonia molecular beam epitaxy depends strongly on the growth temperature TGR. At TGR=760 °C, GaN:Mg films showed a hole concentration of p=1.2 × 1018 cm−3 for [Mg]=4.5×1019 cm−3, while at TGR=840 °C, p=4.4×1016 cm−3 for [Mg]=7×1019 cm−3. Post-growth annealing did not increase p. The sample grown at 760 °C exhibited a low resistivity of 0.7 Ωcm. The mobility for all the samples was around 3−7 cm2/V s. Temperature-dependent Hall measurements and secondary ion mass spectroscopy suggest that the samples grown at TGR>760 °C are compensated by an intrinsic donor rather than hydrogen.