Electronic structure of the 0.88-eV luminescence center in electron-irradiated gallium nitride

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].