A comparative study on the optical and electrical properties of Si-doped polar and nonpolar GaN

Si-doped polar (c-plane) and nonpolar (a-plane) GaN layers grown by metal-organic vapor phase epitaxy (MOVPE) were comparatively investigated using photoluminescence (PL) and Hall-effect measurements. While c-plane GaN revealed both band-acceptor and donor-acceptor transitions, the PL spectra for a-plane GaN were related to extended defects such as basal stacking faults (BSFs) and prismatic stacking faults (PSFs). A new emission peak was observed at 3.361 eV in the Si-doped a-plane GaN, which was attributed to Si-doping-induced defects. The temperature-dependent Hall-effect measurements showed that for c-plane GaN, mobility was dominated by optical phonon and ionized impurity scattering at high and low temperature, respectively. Conversely, for a-plane GaN, the scattering mechanism due to dislocations was dominant at all temperatures.