High‐performance a‐SiGe:H thin film prepared by plasma‐enhanced chemical vapor deposition with high plasma power for solar‐cell application

Hydrogenated amorphous silicon germanium (a‐SiGe:H) thin films were prepared by a 13.56‐MHz plasma‐enhanced chemical vapor deposition (PECVD) method. The optical, optoelectronic, and microstructure properties of the a‐SiGe:H thin films prepared with different plasma powers were investigated systematically by transmission, photo/dark conductivity, Raman, and Fourier transform infrared (FTIR) spectroscopy measurements. It was found that when the deposition pressure was high and the hydrogen (H 2 ) dilution ratio ([H 2 ]/([SiH 4 ] + [GeH 4 ])) was low, an appropriate high plasma power could enlarge the optical bandgap ( E g ) by reducing the Ge content in the thin film, enhance the film photosensitivity by improving the film microstructure, and increase the film growth rate. As a demonstration, excellent a‐SiGe:H thin film with E g of 1.5 eV, the photosensitivity of above 10 4 and a growth rate of 6.6 Å s −1 was successfully fabricated for the solar‐cell application with a plasma power density of 400 mW cm −2 , a deposition pressure of 3 Torr, and a H 2 dilution ratio equal to 3 at 220 °C. The underlying mechanism was further analyzed.