We have investigated point defects in GaN grown by HVPE by using steady-state and time-resolved photoluminescence (PL). Among the most common PL bands in this material are the red luminescence band with a maximum at 1.8 eV and a zero-phonon line (ZPL) at 2.36 eV (attributed to an unknown acceptor having an energy level 1.130 eV above the valence band), the blue luminescence band with a maximum at 2.9 eV (attributed to Zn_Ga), and the ultraviolet luminescence band with the main peak at 3.27 eV (related to an unknown shallow acceptor). In GaN with the highest quality, the dominant defect-related PL band at high excitation intensity is the green luminescence band with a maximum at about 2.4 eV. We attribute this band to transitions of electrons from the conduction band to the 0/+ level of the isolated C_N defect. The yellow luminescence (YL) band, related to transitions via the −/0 level of the same defect, has a maximum at 2.1 eV. Another yellow luminescence band, which has similar shape but peaks at about 2.2 eV, is observed in less pure GaN samples and is attributed to the C_NO_N complex. In semi-insulating GaN, the GL2 band with a maximum at 2.35 eV (attributed to V_N) and the BL2 band with a maximum at 3.0 eV and the ZPL at 3.33 eV (attributed to a defect complex involving hydrogen) are observed. We also conclude that the gallium vacancy-related defects act as centers of nonradiative recombination.

Date Published: 13 March 2015
PDF: 7 pages
Proc. SPIE 9363, Gallium Nitride Materials and Devices X, 93630L (13 March 2015); doi: 10.1117/12.2077002

Published in SPIE Proceedings Vol. 9363:
Gallium Nitride Materials and Devices X
Jen-Inn Chyi; Hiroshi Fujioka; Hadis Morkoç, Editor(s)