关键词: stability of a-Si:H thin film, TLAH, extended exponential law

Abstract: To Investigate the stability of hydrogenated amorphous silicon (a-Si:H) films, the thermal and light-induced annealing treatment in an atomic hydrogen atmosphere (TLAH) is carried out by using a new hot-wire-assisted microwave electron-cyclotron-resonance chemical vapour deposition system (H-W-ECR CVD) modified from a conventional microwave electronic cyclotron resonance chemical vapor deposition system (MWECR CVD). In order to compare with the TLAH method, the experiments of thermal annealing, and thermal and light-induced annealing are also performed. Meanwhile, for the purpose of analysing the photoconductivity degradation quantitative, the photoconductivity degradation is assumed to obey the extended exponential law: 1/$\sigma _{\rm ph}$=1/$\sigma _{\rm s}$-(1/$\sigma _{\rm s}$-1/$\sigma _{0})\exp[-(t/\tau )^{\beta }$], where the extended exponential $\beta $ and the time constant $\tau $ are gained by the slope and the intercept of the line according to the linear relationship between $\ln \left( { - \ln \left( {\dfrac{\sigma _{\rm s}^{ - 1} - \sigma _{\rm ph}^{ - 1} }{\sigma _{\rm s}^{ - 1} - \sigma _0^{ - 1} }} \right)} \right)$ and ln$t$, deduced from the extended exponential law; the photoconductivity saturation value $\sigma _{\rm s}$ can be obtained by Gaussian fitting according to the relationship between photoconductivity and light-soaking time in the logarithmic coordinate system. The experimental results show that the TLAH can improve the stability, microstructure and opto-electronic properties of the annealed a-Si:H films, obviously decrease their optical band gaps, and remarkably move their photoluminescence spectrum (PL) peaks toward low energies.

Key words: stability of a-Si:H thin film, TLAH, extended exponential law