Monolithically Integrated Germanium Photodetector and Planar Antenna for Millimeter‐Wave Transmission

ABSTRACT We present a millimeter‐wave (mm‐wave) emitter featuring a monolithically integrated, high‐performance germanium (Ge) photodetector (PD) coupled with an impedance‐matched on‐chip antenna on a silicon photonic platform. Utilizing the standard multilayer electrode fabrication process in silicon photonics, we design the on‐chip antenna in the upper metal layer. We make specific adjustments to the shape and size of the antenna excitation ports and the intermediate metal layer electrode leads based on the structure of the output electrodes of the Ge detector. This constitutes a substantial breakthrough compared to the traditional bowtie antenna designs that do not include routing plans. The Ge PD exhibits a dark current of 273 nA and a responsivity of 0.86 A/W at a bias of −2 V, ensuring the high system's sensitivity and energy efficiency. Additionally, a high‐resistance silicon lens further strengthens the antenna's directional radiation and gain. The mm‐wave emitter achieves a power output of 10.6 nW at an antenna resonance frequency of 34.96 GHz, measured at a distance of 10 cm without an external amplifier. This integrated mm‐wave emitter is particularly suitable for on‐chip and inter‐chip wireless links for high‐bandwidth data transfer in densely integrated microwave photonic systems. The monolithic integration significantly reduces parasitic losses and enables scalable deployment of antenna–PD units in future silicon photonic platforms.