PHOTOGENERATION AND RECOMBINATION OF CARRIERS IN HYDROGENATED AMORPHOUS-SILICON GERMANIUM ALLOYS

The spectral dependence of carrier generation and recombination loss i n a-SiGe:H samples having band gaps between 1.74 eV and 1.35 eV was st udied in the Schottky barrier solar cell device structure. The active a-SiGe:H layers were of identical thickness (1 mum). The effect of hyd rogen dilution of the source gases (silane and germane) on the generat ion and recombination characteristics was also studied. It has been ob served that the net optical generation of carriers increases almost li nearly with the lowering of the band gap but is independent of the loc alised states. Net recombination loss, on the other hand, increases wi th defect states but cannot be fully explained by taking into account the neutral defect centers alone. Within the above mentioned band gap range, it has been observed that the competing processes of generation and recombination resulted in a maximum short circuit current for a-S iGe:H samples of 1.44 eV band gap.