Ge-on-si photodetector with enhanced optical responsivity by advanced metallization geometry

—In this study, a 1550-nm Ge-on-Si photodetector coupled with a Si waveguide on silicon-on-insulator (SOI) platform has been fabricated and characterized with a particular emphasis on the back-end-of-the-line (BEOL) process. A comparison study of the effects of different metallization schemes on the responsivity has been conducted. Compared to the photodetector with a bulk metal contact, those with single-layered and double-layered contact-hole arrays demonstrated improvements in the optical responsivity at an operating voltage of 1 V. Especially, double-layer scheme showed prominent increase in photon-induced current without significant increase in dark current.