The defect luminescence spectrum at 0.9351 eV in carbon-doped heat-treated or irradiated silicon

Abstract

The electron-vibronic band with its no-phonon (NP) transition at 0.9351 eV which was recently detected in heat-treated silicon is strong after irradiation of silicon and has been studied in high-resolution photoluminescence. The defect exhibits a quasi-local mode of quantum energy h(cross) omega =66.3 meV which is observed as one- and two-phonon vibronic sidebands. The existence of an electronic excited state at an energy of 1.8 meV in excess of the upper level of the NP transition is demonstrated by temperature-controlled experiments. Uniaxial stress and Zeeman measurements show that the defect possesses rhombic I (C_2v) point group symmetry, and that the NP line is a 'spin-1/2 to spin-1/2' ( Gamma ₅ to Gamma ₅) transition. The stress response is nonlinear due to the mixing of the two electronic states by the perturbation. Piezo-optical splitting and interaction parameters are determined. The g-values are g_isotropic=2 for one level of the NP line and g_x=3.65, g_y=1.5 and g_z=0.8 for the other level suggesting that the defect is a pseudo-donor with a tightly bound hole and a loosely localised electron. A carbon isotope effect is observed in the NP transition and in the local-mode satellite giving evidence that one carbon atom per optical centre is involved. Sample statistics and a boron-specific vibronic satellite (h(cross) omega =29.4 meV) suggest that boron is also involved.