Zero bias PIN photodetector based on gradient band distribution and doping gradient profile

Zero bias photodetector which was suitable for top-illuminated and side-illuminated was fabricated. Maximal bandwidth-efficiency product (BEP) value could be achieved when the epitaxial layer structure was optimized. The 3-dB bandwidth of the zero bias was 12.27 GHz, which was numerically above 80% of that maximum value. The measured external quantum efficiency of the photodetector was 17% at the zero bias and 1550 nm. The dark current of the photodetector with 12-μm diameter was less than 9 × 10^?8 A at a reverse bias of 0.1 V. The influence of doping gradient profile on photodetector performance was illustrated by simulation comparison. The important aspects of the design of the high-speed low-bias photodetector were explained. The phenomenon of the photodetector at the reverse bias which was not the higher the better was explained. The improvement in performance of the photodetector was discussed. The fabrication process and the testing process were described in detail.