High-performance Ge-on-Si photodetector with optimized DBR location

We investigated the Ge-on-Si photodetector's performance enhancement by optimizing the detector length, therefore, the location of the distributed Bragg reflector (DBR). Since the unabsorbed signal light in the photodetector oscillates between the germanium and silicon layers, but the DBR is on the silicon layer, the optimized location of the DBR will result in shorter devices, with increased bandwidth, reduced dark current, and consistent responsivity. The 5 μm long photodetector with an optimized DBR location shows responsivity of 0.72 A/W, at least 31.7 GHz 3 dB bandwidth; the dark current is only 7 nA at 1550 nm.