GeSn Avalanche Photodiode

The goal of the project is to develop a novel separate absorption and charge multiplication (SACM) avalanche photodiode (APD) operating at wavelengths of 2 um and even longer.  The proposed APD can achieve high performance at significantly low cost using GeSn absorber material grown by an industry manufacture chemical vapor deposition reactor and a foundry material growth operation mode.  It targets to be used in eye-safe and low-cost LIDAR systems.  The key enabling factors for the new APD over current sensors for LIDAR applications are based on two appealing GeSn material properties: whole short-wave infrared (SWIR) range and even longer wavelength coverage using band-to-band transitions; material growth below 400° C for full complementary metal–oxide–semiconductor (CMOS) compatibility.  The key concepts of the proposed SACM GeSn APD are: i) utilizing GeSn as the front-end light absorber due to the high absorption beyond Ge band edge by incorporating Sn to cover the whole SWIR band; ii) utilizing the excellent multiplication property of Si with the low ionization ratio for low excess noise; iii) leveraging mature Ge/Si SACM APD design; iv) leveraging the recent advances of GeSn material development accomplished by the world leading experts in the team.  In Phase I, the team focuses on feasibility study of the proposed GeSn/Si APD.  The work plan includes: i) modeling GeSn photodiode (PD) and APD devices, since high performance GeSn PD is the foundation of GeSn APD  and effective modeling is the foundation of high performance GeSn PD; ii) evaluating material growth and characterization feasibility for basic APD building blocks; iii) evaluating developing strategy for high performance GeSn PD and specially forming strategy to achieve low dark current; iv) evaluating GeSn APD development strategy to build surface illuminated and waveguide based devices; v) developing Phase II working schedule to accommodate the foundry material growth operation mode.