Ultrahigh-Power Germanium Photodetector Enabling Amplifier-Free Wireless Communication

Abstract

Photodetector (PD), an indispensable component in radio-over-fiber (RoF) systems, functions as an interface between the optical fiber backbone and the wireless radio branches. The power-handling capability is paramount to determine both coverage and linearity of the RoF link, and it is predominantly constrained by the space-charge effect that limits output photocurrent. Consequently, electronic power amplifiers are required to ensure reliable wireless coverage for end-users, albeit at the expense of degraded signal linearity, increased energy consumption, and bulky system. On the other hand, the increasing demand in co-integration with silicon microelectronics indicates that CMOS-compatible germanium-silicon (Ge─Si) PDs hold significant promise. Herein, an ultrahigh-power Ge─Si PD is designed and implemented with an unprecedented high saturation photocurrent of 471.4 mA and a responsivity of 1.12 A W⁻¹. The remarkable high-power performance is achieved through enhancing optical power absorption and promoting photo-generated carrier transit comprehensively. For a proof-of-concept demonstration, amplifier-free wireless communication is achieved and driven by the proposed PD, enabling a range-capacity product of 20 m·Gb s⁻¹, a third-order output intermodulation power of 32.3 dBm at 5 GHz, along with a real-time video stream transmission. This work exhibits a promising solution for on-chip ultrahigh-power photodetection, and represents a significant advancement toward high-quality fiber-wireless access network.