Silicon-Integrated High-Speed Graphene Hot Electron Light Emitters

Silicon-integrated graphene devices have enabled high-speed photodetectors and modulators, yet a monolithic graphene light source─a crucial missing component for full photonic integration─has remained elusive, fundamentally limited by graphene’s gapless electronic structure. Here, we demonstrate electrically driven, high-speed graphene hot electron light emitters based on suspended graphene/hexagonal boron nitride heterostructures monolithically integrated on a silicon photonics platform. We show that the broadband blackbody radiation from the heterostructure can be efficiently coupled into a silicon waveguide through a designed grating coupler, achieving a coupling efficiency of 24.7% at the telecom wavelength of 1550 nm. Under electrical excitation, the device generates optical pulses with modulation speeds up to 0.7 GHz. The unusually high modulation rate of thermal emission is attributed to the weak coupling between the hot electrons and acoustic phonons in the suspended stack. Furthermore, by cointegrating the emitter with a germanium photodetector on the same chip using back-end-of-line-compatible processes, we realize a fully monolithic optical transceiver operating at 100 MHz bandwidth. This work establishes a pathway toward multifunctional graphene-based photonic systems, where light emission, detection, and modulation can be implemented on a single graphene/silicon heterostructure platform, opening routes to reconfigurable and dense silicon photonic circuits.