THE EFFECT OF Ge CONTENT ON THE OPTICAL AND ELECTRICAL PROPERTIES OF a-SiGe:H THIN FILMS

The effect of Ge content on the optical and electrical properties of Si-Ge-H thin films deposited by HWCPECVD had been investigated. The Si- Ge-H films ware grown on corning glass 7059 substrate using 10% diluted GeH4 and SiH4 gas mixture, respectively. The GeH4 gas flow rate was varied from 2.5 to 12.5 sccm, while the flow rate of SiH was kept constant at 70 sccm. The results showed that the deposition rate of Si-Ge-H thin films was increases with the increasing of GeH4 gas flow rate. Beside, the Ge content in the film also increased, and the optical band gap decreased. The dark conductivity of Si- Ge-H films was relatively constant, whereas the photo ’s conductivity decreased with increasing of Ge content.