Vol. 55, Issue 1, pp. 33-48 (2025)

Abstract

We report a novel mushroom-typed modified near-ballistic uni-traveling-carrier photodetector (modified NBUTC-PD) based on a drift-diffusion model which achieves high responsivity at the sub-THz regime. By well-designed active and depleted regions to form a “mushroom” type, with the optimal cliff and charge layers to make electrons transport at a “near-ballistic” speed, of order 10⁷ cm/s, as well as the rational hybrid-doping absorber, the modified NBUTC-PD successfully achieves the decoupling between the bandwidth and responsivity characteristics. For the modified NBUTC-PD with an active area of 12.56 μm², the simulation shows that the 3-dB bandwidth is up to 107 GHz, with a responsivity up to 0.38 A/W, at a reverse bias voltage of 1 V. The decrease in 3-dB bandwidth of the modified NBUTC-PD is analysed in detail under high-light injection conditions, which results from the energy band shift and electric field collapse.