Photoluminescence properties of a-SiN_x: H alloys

Abstract

Photoluminescence (PL) studies are reported on a series of a-SiN_x:H alloys prepared by glow discharge, with x up to around 1·1. As x increases, the main PL band broadens and moves to higher energies, and there is a marked reduction in the temperature dependence of the PL efficiency, linewidth and peak energy. The 0·9 eV defect band increases by a small factor and there is only a small reduction in the efficiency of the main band, strongly suggesting that nitrogen introduces few extra dangling-bond defects. Excitation studies show a strikingly large red-shift at low excitation energies up to 0·5eV or more in SiN_1·1. This suggests a large increase in tail-state widths, probably due to compositional fluctuations, and this is consistent with most of the other changes in PL behaviour with alloying. We also compare our data briefly with PL from a-Si/SiN_x multilayers.