Simulation study of high-speed Ge photodetector dark and light current degradation

Wednesday,  march 23, 2022  at 1pm
 

        Data communication is largely dependent on fiber optic networks due to high throughput and efficient transmission to greater distances. Over the decades, silicon semiconductor technology has been well established in fabricating electronic integrated devices, circuits and optic waveguides. The semiconductor technology to support this platform consists in semiconductor lasers, waveguides, modulators, mixers, light couplers and detectors. The high-speed Ge photodetector studied in this work is fabricated using conventional planar silicon device technology. This Si photonic device is almost a system on chip that integrates photonics and electronics in one wafer. Hence the hurdles in improving these device performance, lifetime and maintenance are almost the same as silicon technology.
         In this project, the reliability of Ge photodetectors used in the framework of Si photonics is studied using TCAD simulation. This work mainly focuses on simulation, in order to better understand the physical origin of dark current and responsivity degradation, which was previously observed in stressed reliability experiments. It is shown that bulk and interface recombination mainly modify the SRH dominated dark and light currents, while fixed charge and Dit 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.