由缺陷引起的Burstein-Moss和带隙收缩效应对CdIn_2O_4透明导电薄膜光带隙的影响

Effect on optical band-gap of transparent and conductive CdIn_2O_4 thin film due to defects-induced burstein-moss and band-gap narrowing characteristics

在Ar+O2 气氛 ,采用射频反应溅射Cd In靶制备CdIn2 O4 (CIO)薄膜 .通过对不同衬底温度下制备和沉积后在氩气流中退火的薄膜进行透射、反射和Hall效应的测量和分析发现 ,随着衬底温度的降低 ,载流子浓度呈上升趋势 ,而吸收边呈现先是“蓝移”然后“红移”的现象 .从理论上阐述了高浓度的点缺陷对CIO氧化物薄膜的能带产生的重要影响 ,这些影响主要体现在带尾的形成 ,Burstein Moss(B M)漂移和带隙收缩 .另外 ,衬底温度的变化将对薄膜的迁移率有重要影响 .对于CIO薄膜 ,由缺陷产生的空穴浓度将对薄膜的带隙收缩产生重要影响并将直接影响到薄膜的光透性 .由于存在吸收带尾 ,利用传统的“外推法”获得薄膜的光带隙并不适合简并半导体 ,而应使用更为准确的“拟合法” .

Transparent and conductive oxides CdIn2O4(CIO) thin films were prepared by RF reactive sputtering from a Cd-In alloy target in Ar + O2 atmosphere. By the analysis and measurements of transmittance spectra and Hall-effect of different samples prepared at different substrate temperatures and post-deposition annealing in an Ar gas flow, it was found that the carrier density increases with the decrease of substrate temperature, but the absorption edge shows an abrupt change from a blue-shift to a red-shift. Theoretically, the paper formulated the effect on band structure due to higher density of point defects, it embodies the band-tailing, Burstein-Moss (B-M) shift and band-gap narrowing. In addition, density of ionized impurity substrate temperature induced will affect the carrier mobility. The hole density impurity-induced will influences the magnitude of optical band-gap and transmittance of light. Since extrapolation method does not fit degenerate materials, a more accurate method of obtaining band-gap is the method of curve fitting.