Toward photodetection at 2 μm wavelength band: GeSn/Ge multiple-quantum-well photodetectors integrated on Si substrates

Optical detection at 2-μm wavelength spectral range has recently attracted increasing attention for many important applications. This can be done using narrow-bandgap III-V or II-VI based semiconductor photodetectors (PDs). Here, we report on group-IV based GeSn/Ge multiple-quantum-well (MQW) photoconductive photodetectors (PDs) for optical detection at the 2μm wavelength band. By introducing Sn into the well, the direct bandgap is reduced, thereby extending the absorption edge into longer wavelengths. The optical responsivity measurements reveal that the detection of the fabricated PDs is extended beyond 2000 nm. These results demonstrate the feasibility of GeSn/Ge MQW PDs for optical detection at the 2μm wavelength band.