SPIN-DEPENDENT PHOTOCONDUCTIVITY IN HYDROGENATED AMORPHOUS-SILICON GERMANIUM ALLOYS

We use spin-dependent photo-conductivity (SDPC) to study the recombination process of photo-excited carriers in hydrogenated amorphous silicon germanium alloys (a-SixGe1-x:H). The incorporation of Ge is marked by a sudden change in the SDPC signal ( -Delta sigma/sigma ) from (a-Si:H)-like to (a-Ge:H)-like. The Ge atoms create new states which dominate transport and recombination of photo-created free carriers. In particular, the SDPC lineshape analysis indicates that the a-Si:H conduction band tail is affected by alloying with small concentrations of germanium.