Erich Kasper

GeSn photodetectors with Sn contents between 0% and 6.5% were grown pseudomorphically on Ge virtual substrates on Si by molecular beam epitaxy. Based on the similar functional dependence of the current-voltage characteristics, we conclude that a similar crystal defect is the cause of the recombination/generation centers in both the GeSn and the Ge reference sample. We found that dislocations are not the predominant recombination type. The signal-to-background ratio is a proper quantitative measure for the comparison of heterostructure photodetectors and with near zero bias operation in the C-band, the values of around 104 were obtained with 1 mW light input. For C-band operation, the optimal Sn contents are found to be between 2% and 4%.