High-efficiency normal-incidence vertical p-i-n photodetectors on a germanium-on-insulator platform

In this paper, normal incidence vertical p-i-n photodetectors on a germanium-on-insulator(GOI) platform were demonstrated. The vertical p-i-n structure was realized by ion-implanting boron and arsenic at the bottom and top of the Ge layer, respectively, during the GOI fabrication. Abrupt doping profiles were verified in the transferred high-quality Ge layer. The photodetectors exhibit a dark current density of ~47 mA∕cm~2 at-1 V and an optical responsivity of 0.39 A/W at 1550 nm, which are improved compared with state-of-the-art demonstrated GOI photodetectors. An internal quantum efficiency of ~97% indicates excellent carrier collection efficiency of the device. The photodetectors with mesa diameter of 60 μm exhibit a 3 dB bandwidth of ~1 GHz, which agrees well with theoretical calculations. The bandwidth is expected to improve to ~32 GHz with mesa diameter of 10 μm. This work could be similarly extended to GOI platforms with other intermediate layers and potentially enrich the functional diversity of GOI for near-infrared sensing and communication integrated with Ge CMOS and mid-infrared photonics.