Photobleaching of PL and temperature dependence of ESR in nitrogen-rich amorphous silicon nitride films

Abstract

We report measurements in nitrogen-rich a-SiNx:H (x > 1.3) of visible light photobleaching of photoluminescence (PL) that has been fatigued with UV light. We also review the temperature dependence of electron spin resonance (ESR) from a-SiN1.6:H films. The samples were prepared by plasma-enhanced chemical vapor deposition (PECVD) at 400 and 250°C. The optical gap of a-SiN1.6:H is about 5 eV. In PL experiments, the PL intensity fatigues under UV excitation, finally reaching a saturated value. By illuminating with visible light, the UV effect is partially bleached, that is, the PL intensity is partially restored. The bleaching light ranges in energy from 2.0 to 4.8 eV. With increasing bleaching-light energy, the reinduced PL intensity increases, reaches a maximum at a bleaching energy of 3.8 eV, and then quickly decreases. In ESR experiments, there exists a small ESR signal in as-deposited films before UV excitation and the variation of the ESR signal with temperature is similar to that of a-As. © 1994 Materials Research Society.