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 10 4 cm −2 and less than 10 0 cm −1 , respectively. Oxygen doping achieved a high electron concentration of 4 × 10 18 cm −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 low-level incorporation of Ga vacancies (V Ga ) less than 10 16 cm −3 was confirmed by using the positron annihilation technique. Consistent with our long-standing claim that V Ga 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.