Near-infrared photodetectors in evaporated ge: Characterization and TCAD simulations

Thermal evaporation of germanium (Ge) on silicon (Si) has proved to be a suitable technique for the fabrication of high responsivity, low-cost, near-infrared pn detectors. Such results rely on low-temperature diffusion of n-type dopants. The corresponding transport phenomena are quite involved and cannot be described by standard models for pn junctions because of rather large defect concentration density in the Ge layer. In this paper, we report on fabrication, characterization, and simulation of defected Ge on Si photodiodes. For the simulations, we developed a technology computer aided design model and hereby demonstrate its ability to reproduce the measured optoelectronic characteristics of the devices.