Hydrogenated amorphous silicon germanium alloy with enhanced photosensitivity prepared by plasma enhanced chemical vapor deposition at high temperature

Hydrogenated amorphous silicon germanium (a-SiGe:H) alloys were prepared by plasma enhanced chemical vapor deposition (PECVD) at different deposition temperatures. The optical, optoelectronic properties and the microstructure of the prepared a-SiGe:H alloys were investigated systematically by transmission, photo/dark conductivity, Raman, and Fourier transform infrared (FTIR) spectroscopy measurements. The Ge atom content was further determined by energy dispersive spectroscopy (EDS) and the surface roughness was checked by atomic force microscopy (AFM). It was found that the narrow bandgap (Eg) a-SiGe:H alloy with the enhanced photosensitivity (Ratio of photo conductivity to dark conductivity) and the rapid growth rate could be prepared when the deposition temperature was relatively high. The underlying mechanism was analyzed carefully. The results indicated that high temperature deposition might be an effective way to prepare a-SiGe:H alloys for solar cell application.

► High deposition temperature resulted in low Eg and high growth rate for a-SiGe:H.
► The a-SiGe:H photosensitivity was also enhanced by high temperature deposition.
► High photosensitivity was attributed to the microstructure modification.
► Eg of 1.55 eV and photosensitivity of 104 were obtained at 310 °C for a-SiGe:H.