摘要
研究了衬底温度（Ｔｓ）从室温至６２３Ｋ生长的氢化非晶硅（ａ—Ｓｉ：Ｈ）的光电导的温度依赖关系，首次发现了出现光电导的热淬灭（ＴＱ）的温度区随ａ—Ｓｉ：Ｈ的Ｔｓ的降低系统地移向较低温度区．分析了ａ—Ｓｉ：Ｈ中这种新现象与费米能级位置以及能隙中缺陷态密度分布的关系．
it is well known that the photoconductive performance is often used to roughly characterize the quality of amorphous semiconductors. The photoconductivity is dependent on many conditions, such as light intensity, dooping levels. In this paper, we report for the first time that photoconductivity of hydrogenated amorphous silicon (a-Si:H)is sensitive to substrate temperature (Ts).a-Si:H films were deposited by an r. f. plasma enhanced chemical vapor deposition (PECVD) technique in a capacitively coupled single reaction chamber. All fims were made form Argon diluted silane gas and deposited on Corning 7059 glasses and fused quartz at different Ts from 300K to 623K.The temperature dependence of photoconductivity (σp) of a-Si:H films can be divided into three regions: (1) at low temperature (T< 70K),σP is nearly constant; (2) at intermediate temperature,σp rises with T by several orders of magnitude; and (3) at high temperature (T>250K),σp decreases with increasing T and again rises till the concentration of thermal equilibrium carriers is comparable to one of photo-excited carriers. We have explored the new phenomenon of thermal quenching in high temperature region. When Ts is between 373K and 523K, the temperature region of thermal quenching of thephotoconductivity is systematic shift to the lower temperature region with decreasing Ts.When Ts is as high as 623K or low as 300K, no thermal quenching occurs, but it exists inthe region whereσP keeps mearly constant.The position of Fermi level and distribution of defect states in the mobility gap aresensitive to Ts. When Ts rises, Ef shifts towards conductive band and the density of defect states decreases. This relationship causes the systematic shitl of thermal quenching.
出处
《南京大学学报（自然科学版）》
CSCD
1995年第1期20-24,共5页
Journal of Nanjing University（Natural Science）
基金
国家自然科学基金
关键词
氢化非晶硅
光电导
热淬灭
非晶态半导体
hydrogenated amorphous silicon, photoconductivity, thermal quenching
