Optical and electronic characterization of a-SiGe:H thin films prepared by a novel hollow cathode deposition technique

Using a novel hollow cathode plasma-jet reactive sputtering system in which an intense plasma, ignited in an Ar/H₂ flow, is directed through silicon and germanium nozzles, a series of a-SiGe:H thin films have been prepared on silicon and glass substrates. These films have been optically characterized by infrared (IR) spectroscopy and spectroscopic ellipsometry (335-1000nm). Total hydrogen concentrations, as determined by FTIR, varied with deposition conditions and ranged from 2.5 × 10²¹ to 1.6 × 10²² atom cm^-3 and correlated with secondary ion mass spectrometry (SIMS) elemental analyses to within 10%. Conductivity measurements in the dark and under simulated AMI solar illumination have indicated that the films properties are very good. The light to dark conductivity ratio has consistently been greater than 1000 for films with band gaps down to 1.3 eV.