Simulation analysis of combined UV/blue photodetector in CMOS process by technology computer-aided design

摘要

A composite ultraviolet (UV)/blue photodetector structure has been proposed, which is composed of P-type silicon substrate, P_(well), N_(well) and N-channel metal-oxide-semiconductor field-effect transistor (NMOSFET) realized in the P_(well). In this photodetector, lateral ring-shaped P_(well)-N_(well) junction was used to separate the photogenerated carriers, and non-equilibrium excess hole was injected to the P_(well) bulk for changing the bulk potential and shifting the NMOSFET's threshold voltage as well as the output drain current. By technology computer-aided design (TCAD) device, simulation and analysis of this proposed photodetector were carried out. Simulation results show that the combined photodetector has enhanced responsivity to UV/blue spectrum. Moreover, it exhibits very high sensitivity to weak and especially ultral-weak optical light. A sensitivity of 7000 AAV was obtained when an incident optical power of 0.01 μW was illuminated to the photodetector, which is 35000 times higher than the responsivity of a conventional silicon-based UV photodiode (usually is about 0.2 AAV). As a result, this proposed combined photodetector has great potential values for UV applications.