title: Infrared photoresponse of GeSn/n-Ge heterojunctions grown by molecular beam epitaxy.
abstract: Heterojunction devices of Ge(1-x)Sn(x) / n-Ge were grown by solid source molecular beam epitaxy (MBE), and the mid-infrared (IR) photocurrent response was measured. With increasing Sn composition from 4% to 12%, the photocurrent spectra became red-shifted, suggesting that the bandgap of Ge(1-x)Sn(x) alloys was lowered compared to pure Ge. At a temperature of 100 K, the wavelengths of peak photocurrent were shifted from 1.42 µm for pure Ge (0% Sn) to 2.0 µm for 12% Sn. The bias dependence of the device response showed that the optimum reverse bias was > 0.5 volts for saturated photocurrent. The responsivity of the Ge(1-x)Sn(x) devices was estimated to be 0.17 A/W for 4% Sn. These results suggest that Ge(1-x)Sn(x) photodetectors may have practical applications in the near/mid IR wavelength regime.
authors.forename: Sangcheol
authors.initials: S
authors.lastname: Kim
authors.forename: Nupur
authors.initials: N
authors.lastname: Bhargava
authors.forename: Jay
authors.initials: J
authors.lastname: Gupta
authors.forename: Matthew
authors.initials: M
authors.lastname: Coppinger
authors.forename: James
authors.initials: J
authors.lastname: Kolodzey