Honors Project On-Campus Access Only
Hydrogenated amorphous silicon germanium (a-SiGe:H) has important applications in solar cell technology. In order to maximize efficiency of solar cells, the semiconductor materials used in them must have a low defect density. Photoconductivity is sensitive to defect density, so measurements and modeling of photoconductivity are important diagnostics for a-SiGe:H. In this work, the photoconductivity of thin film samples of a-SiGe:H were measured at carrier generation rates for 10(14) to 10 (17) cm(-3)s(-1) and temperatures from 80K to 310K. The experimental data was compared to two numerical models published in the literature. One model, by Shen and Wagner(1), used a simple model for recombination and transport and was reproduced here in (see Appendix) in order to fit the acquired data. The total density of states and distribution in the band gap was varied. However, the model predicted a greater decrease in photoconductivity at low temperatures than was observed in the experimental data for all cases. The second model by Merazga et al (2), which included recombination of electrons and holes and transport in the band tail states, appears to be in better agreement with the data.
Boyer, Hallie C., "Photoconductivity in Amorphous Silicon Germanium Alloys at Low Temperature" (2008). Physics and Astronomy Honors Projects. 5.
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