Electronic and optical characteristics of an m-plane GaN single crystal grown by hydride vapor phase epitaxy on a GaN seed synthesized by the ammonothermal method using an acidic mineralizer

Fundamental electronic and optical properties of a low-resistivity m-plane GaN single crystal, which was grown by hydride vapor phase epitaxy on a bulk GaN seed crystal synthesized by the ammonothermal method in supercritical ammonia using an acidic mineralizer, were investigated. The threading dislocation and basal-plane staking-fault densities of the crystal were around 10⁴cm^-2 and less than 100cm^-1, respectively. Oxygen doping achieved a high electron concentration of 4 ' 10¹⁸cm^-3 at room temperature. Accordingly, a photoluminescence (PL) band originating from the recombination of hot carriers was observed at low temperatures, even under weak excitation conditions. The simultaneous realization of lowlevel incorporation of Ga vacancies (VGa) less than 10¹⁶cm^-3 was confirmed by using the positron annihilation technique. Consistent with our longstanding claim that VGa complexes are the major nonradiative recombination centers in GaN, the fast-component PL lifetime of the near-band-edge emission at room temperature longer than 2 ns was achieved.