Influence of crystalline defects on transport properties of GaN grown by ammonia-molecular beam epitaxy and magnetron sputter epitaxy

GaN layers have been grown using an MBE/MSE (molecular beam epitaxy/magnetron sputter epitaxy) dual-mode system. The layers grown by the two techniques exhibited a large difference in crystalline quality and presented a broad spectrum of structural, optical, and transport properties that are useful for an analysis of the role of crystalline defects in GaN epilayers. The model of electron scattering by charged threading dislocations was applied in a theoretical fit of the mobility data. The theoretical fit in combination with x-ray diffraction and photoluminescence studies reveal the correlation between dislocation density, electron mobility, doping characteristics and yellow luminescence.