Growth of Amorphous Silicon Germanium (a-SiGe:H) Alloys Thin Film by PECVD

Abstract

Hydrogenated amorphous silicon-germanium (a-SiGe:H) alloys thin films had been grown by Plasma Enhanced Chemical Vapor Deposition (PECVD) method. The films were grown on corning glass # 7059 from a gas mixture of silane (SiH4) and germane (GeH₄) 10% diluted in hydrogen (H₂). UV-VIS-NIR spectra analysis of a-SiGe:H alloys thin films showed that the sub-bandgap absorption α(hν) spectra of a-SiGe:H alloys shift to lower photon energy with increasing in GeH4 flow rate. 

The optical bandgap of a-SiGe:H alloy decreased non linearly from 0.94 eV – 0.75 eV with increasing in GeH₄ flow rate from 2.5 sccm – 25 sccm. The photo-sensitivity (σ_ph/σ_d) of a-SiGe:H thin films were improved as the optical bandgap (E_opt) increased.