Simulation Study of High-Speed Ge Photodetector Dark and Light Current Degradation

The reliability of Ge photodetectors used in the framework of Si photonics is studied using TCAD simulation, in order to better understand the physical origin of dark current and responsivity degradation observed in Sy et al. (2019). It is shown that bulk and interface recombination mainly modify the SRH dominated dark and light currents, while fixed charge and $\text{D}_{\mathrm{ it}}$ strongly impacts band-to-band tunneling dark currents. This essential distinction shows the necessity to discriminate the dominating transport mechanisms in photodetectors using activation energy measurement, in order to better identify the origin of performance degradation. It also strengthens the requirement for adequate passivation of all interfaces to reach higher lifetime of photodetectors.