Amorphous Silicon-Germanium Thin Films Prepared By PECVD And Its Properties

The I-layer, which located between P-layer and N-layer in a typical structure of thin-film solar cell, was usually considered as the most critical layer, just for that it was where photo-carrier generated and determined conversion efficiency of the cell. Therefore, the I-layer preparing and relevant technical problems on improvement of long-wave absorptivity and conversion efficiency of thin-film solar cell were studied in this paper.Amorphous silicon germanium thin films were prepared by radio frequency plasma enhanced chemical vapor deposition (RF-PECVD) using 20% purity SiH4 and 99.999% purity GeH4 as reaction gases and 99.99% purity H2 as diluent gases under four different conditions, including reaction gas concentrations, substrate temperature, glow power and reaction gas pressure. Then, some themes about the films, such as structure characteristics, deposition rate, optical band gaps and photosensitivity were discussed in the paper. As the result, the paper came to the following conclusions:a). the deposition rate of films would increase as glow power reduced and reaction gas presure decreased, but it had no significant change when temperature rised or reaction gas concentration increased; b) optical band gaps narrowed as temperature rised and reaction gas concentration increased, meanwhile, it were almost not affected by both glow power and gas presure. Hardly affected by substrate temperature, discharge power gas pressure of reaction, but related closely by the reaction gas density, the photosensitivity increases at first and then decreases following the raising of the gas density.