Influence of absorber layer dopants on performance of Ge/Si single photon avalanche diodes

Monte Carlo electronic transport simulations are applied to investigate the influence of the Ge absorber layer on the performance of Ge/Si single photon avalanche diodes. Ge dopant type and concentration control the internal electric field gradients, which directly influence the probabilistic distribution of times from the point of charge photo-generation to that of transmission over the Ge/Si heterojunction. The electric field adjacent to the heterointerface is found to be the dominant factor in achieving rapid transmission, leading to a preference for p-type dopants in the Ge absorber. The contribution to jitter from the Ge layer is estimated and appears relatively independent of bias, though scales near-linearly with layer height.