Deposition Temperature Dependence of Optical Properties of a-Si:H for Short-wave Near-infrared Filter by DC Sputtering

Abstract

In this study, the deposition temperature dependence of film structures, optical characteristics and thermal durabilities of hydrogenated amorphous silicon (a-Si:H) prepared by dc reactive sputtering were investigated for application to short wave near infrared (SWNIR) band pass filter (BPF). When the deposition temperature was 300℃, a film with a low hydrogen composition and less structural disorder was obtained, and it was found that thermal deteriorations after annealing (300℃, 2 hours) were suppressed. The transmittance of the BPF with stacked a-Si:H and SiO₂ deposited at 300℃ were stabilized after annealing due to the characteristics of a-Si:H. However, the optical extinction coefficient k of a-Si:H became the minimum value at 200℃, and tended to increase as the deposition temperature increased. It may be attributed to the decrease in bandgap and the increase in dangling bonds due to hydrogen thermal desorption confirmed by decreasing of hydrogen composition as deposition temperature increases.