Characterization of high rate a-SiGe:H thin films fabricated by 55 kHz PECVD

An investigation of the influence of substrate temperature on optoelectronic properties and microstructure of a-SiGe:H films fabricated by low frequency 55 kHz PECVD method was carried out. It was found that the decrease of substrate temperature leads to increase of photosensitivity. The IR spectroscopy analysis and modeling of photoconductivity have shown that the clustering of SiH and SiH2 bonds on the surface of island and Si related defects determine the density of states distribution in the mobility gap. The energy band diagram was analyzed and it was shown that density of states distribution does not significantly change with the decrease of substrate temperature, which is attributed to the ion bombardment of the growth surface in low frequency discharge. Thus, 55 kHz PECVD method allows the decrease of the deposition temperature for the fabrication of low band gap a-SiGe:H films with the device quality electronic properties and at high deposition rate. [Copyright &y& Elsevier]