Roles of carbon impurities and intrinsic nonradiative recombination centers on the carrier recombination processes of GaN crystals

The relationship between the concentration of carbon (C) impurity, [C], and quantum efficiency (QE) of radiation in n-type GaN crystals was clarified under photo-excitation conditions at room temperature. Since C acts as a trap for minority holes as well as a compensator for majority electrons, the external QE (EQE) and internal QE (IQE) values for the near-band-edge (NBE) emission showed a monotonic increase with decreasing [C], where NBE EQE (IQE) values are 0.02% (0.70%) and 0.53% (14.2%) for [C] = 2.0 x 10(16) cm(-3) and [C] = 4.0 x 10(14) cm(-3), respectively, under a cw photo-pumping density of 140 W cm(-2). (C) 2019 The Japan Society of Applied Physics.