Optical properties of plasmahyphen;enhanced chemical vapor deposited siliconhyphen;oxynitride films

摘要

By transmission and reflection spectroscopy between 1.5 and 9.5 eV, at 300 and 100 K, we have obtained the absorption coefficient agr; of silicon oxynitride films grown by plasmahyphen;enhanced chemical vapor desposition from gas mixtures of SiH4and N2O at 430thinsp;deg;C. IR, electron spin resonance (ESR), and transport measurements have been performed previously on this sample of SiOxNyHzknown composition by elastic recoil detection analysis (ERDA). The optical gapEG, the slopeBof Taucrsquo;s plot (agr;hngr;)1/2=B(hngr;minus;EG), and the reciprocal slopeEoof the Urbach tail present strong correlation in SiOxNyHzand SiNyHzfilms. Below a percolation limit for oxygen, nitrogen, and hydrogen incorporation in theahyphen;Si amorphous network, the relevant physical parameter for the composition isxin SiOx, (y+z) in SiNyHz, and (x+y+z) in SiOxNyHz. Thus, we find single curves for the variation with the composition ofE04 (the energy at which agr;=104cmminus;1),E0, and 1/B. Above the percolation composition the optical absorption below the principal absorption edge is dominated by defect states in the gap. According to ESR and ERDA measurements, the absorption shoulder between 7 and 8 eV may be explained by the presence of OHminus;or O+3diamagnetic centers in the insulator.