In this work, we present a novel avalanche photodiode (APD) that utilizes the \({\text{Si}}_{1-\text{x}}{\text{Sn}}_{\text{x}}\) -on-silicon (SiSn-on-Si) platform to enable short-wave infrared (SWIR) operation. This work reports the first proof of the \({\text{Si}}_{1-\text{x}}{\text{Sn}}_{\text{x}}\) alloy-based APD. Here, we propose two device structures—p+-i-p-i-n+ (device D1) and n+-i-n-i-p+ (device D2)—and we use COMSOL Multiphysics to analyze their performance. With the insertion of Sn into the \({\text{Si}}_{1-\text{x}}{\text{Sn}}_{\text{x}}\) alloy, the bandgap energy decreases, and the detection wavelength is redshifted toward a longer wavelength. As a result, this work presents the breakthrough of Si-based detectors, demonstrating significant advancements in the field. Moreover, the high absorption coefficient of the \({\text{Si}}_{1-\text{x}}{\text{Sn}}_{\text{x}}\) alloy over pure Si results in high responsivity. The separate absorption, charge, and multiplication (SACM) device structure allows for a substantial performance improvement, with device D1 achieving a high multiplication gain of over 77 and device D2 achieving a multiplication gain of over 80 at a wavelength of 1310 nm and a temperature of 300 K. Our proposed SiSn-on-Si APD shows a significant reduction in excess noise factor compared to the In0.52Al0.48As device. In addition, when compared to previously reported Si/Ge APDs, the SiSn-on-Si APD demonstrates superior performance in terms of gain, responsivity, and the low bias voltage required for operation. These findings, using the cost-effective SiSn-on-Si platform, provide a pathway for the future development of high-performance Si-based APDs for use in the SWIR bands.
