Silicon-integrated SWIR and MWIR GeSn photoconductive devices

SWIR and MWIR photodetector technologies are mainly served by III-V and II-VI materials such as InSb, InGaAs, and HgCdTe which are costly, require cooling, and face manufacturing and scalability challenges. GeSn is an attractive group IV material that is Si-compatible with the potential to circumvent these challenges by enabling the fabrication of SWIR and MWIR detectors on a scalable and cost-effective Si platform. In this work, material development and optoelectrical properties of a set of heterostructures made of Si/Ge/GeSn are presented. The material properties and its potential application in photodetectors are discussed. For instance, at a low Sn content (below 5 at.%), we found that GeSn-based photoconductive devices display unexpectedly a low dark current and exhibit a room-temperature cutoff wavelength of 1.75 um and a responsivity of 0.52 A/W at 1.55 um. Results from microscopic and spectroscopic studies are also presented. Finally, capacitance devices are fabricated to extract unintentional doping concentrations from CV measurements.