Cascade Uni-Traveling-Carrier Photodetector Array for Terahertz Applications

A cascade array structure and depleted layer thickness design method of uni-traveling-carrier photodetector (UTC-PD) for terahertz applications is proposed. The cascade array structure can increase the 3dB bandwidth from 203 GHz to 255 GHz compared to the high-speed single UTC-PD with a diameter of $3 ~\mu \text{m}$ by effectively reducing the overall device capacitance. The 3dB bandwidth can be further improved to 267 GHz by thickness optimization. The combination of cascade array structure and depleted layer thickness optimization can significantly improve the saturation output power of the device at 100, 200 and 300 GHz, which enables the design of cascade UTC-PD array to be applied in terahertz (THz) band.