Design of GeSn single photon avalanche photodiodes for short wave infrared detection

There is a desire for single photon avalanche diodes (SPADs) capable of detecting light in the SWIR wavelength range for Lidar systems to increase their range while maintaining eye safety. It is also desirable for these SPADs to be CMOS compatible. Ge-on-Si SPADs have been demonstrated by several groups, but Ge only extends the wavelength response to around 1.6 μm. This paper investigates the design of SPADs using GeSn as an absorber to increase the wavelength response to 2 μm. We will compare the use of Si and Ge as a material for the multiplication region.