Analysis of Mg-related emissions in p-GaN grown by MOCVD

We have investigated the Mg-related emissions of the p-GaN layer grown by metalorganic chemical vapor deposition using Raman scattering and photoluminescence (PL) experiment. The E-2 (LO) mode in the Raman scattering was found to be the blueshift of 2.29 cm(-1) in comparison with that of the undoped GaN. This may be associated with the stress increment induced by the doping of Mg. The Mg-related emissions observed in the PL results are related to the deep DAP emission due to the transitions from deep donor levels of 0.14, 0.26, 0.4, and 0.58 eV below the conduction band to the shallow Mg acceptor level of 220 meV upper the valence band. Also, the Mg-related emission localized at 2.737 eV tended to quench the intensity and extend the emission linewidth with increasing temperature. This quench process is considered to be related to the vibration mode of LO phonon. Based on the two-step quenching process model and Toyozawa's theory, the activation energy and the average energy were estimated. (C) 2003 Elsevier B.V. All rights reserved.