Energy balance modeling of Ge-on-Si waveguide avalanche photodetectors

Commercial CAD tools for carrier transport simulation in optoelectronic devices are commonly based on the drift-diffusion (DD) model. In the design of silicon photonics optical interconnects, the DD approach can be acceptable for p-i-n photodetectors, but may be inadequate for avalanche photodiodes (APDs). Here we discuss the DD limitations in the case of waveguide Ge-on-Si SACM APDs, and we investigate the advantages and shortcomings of higher-order descriptions, with particular attention to the energy balance model.