Ia. Buyanova et al., Electronic structure of the 0.88-eV luminescence center in electron-irradiated gallium nitride, PHYS REV B, 60(3), 1999, pp. 1746-1751
Photoluminescence (PL) spectroscopy is employed to determine the nature of
a near-infrared PL emission with a no-phonon line at similar to 0.88 eV, co
mmonly present in electron-irradiated GaN. This PL emission is suggested to
originate from an internal transition between a moderately shallow excited
state (with an ionization energy similar to 21 meV) and the deep ground st
ate (with an ionization energy similar to 900 meV) of a deep defect. The ex
istence of a higher-lying second excited state related to the 0.88-eV PL ce
nter is also shown from temperature-dependent studies. A different electron
ic character of the wave functions related to the first and second excited
states has been revealed by PL polarization measurements. Since the PL emis
sion has been observed with comparable intensity in all electron-irradiated
CaN samples independent of doping on the starting material, it is proposed
that either native defects, or common residual contaminants or their compl
exes are involved. The substitutional O-N donor (or related complex) is con
sidered as the most probable candidate, based on the observed striking simi
larity in the local vibrational properties between the 0.88-eV PL centers a
nd the substitutional O-p donor in GaP. [S0163-1829(99)13027-3].