Si-Based GeSn Photodetectors toward Mid-Infrared Imaging Applications

The GeSn detector offers high-performance Si-based infrared photodetectors with complementary metal-oxide-semiconductor (CMOS) technique compatibility. In this work, we report a comprehensive study of Si-based GeSn mid-infrared photodetectors, which includes the demonstration of a set of photoconductors with Sn compositions ranging from 10.5% to 22.3%, showing the cutoff wavelength has been extended to 3.65 μm. The maximum D* of 1.1 × 1010 cm·Hz1/2·W–1 measured at 77 K is comparable to that of commercial extended-InGaAs detectors. We also report the development of a surface passivation technique on photodiodes based on an in-depth analysis of a dark current mechanism, effectively reducing the dark current. Moreover, mid-infrared images were obtained using GeSn photodetectors, showing the comparable image quality with that acquired by using commercial PbSe detectors. This work is a major step toward Si-based mid-infrared photodetectors for imaging applications.