Mechanism and Optimization of a Graphene/Silicon Hybrid Diode Terahertz Modulator

Graphene/silicon hybrid diodes have been proven efficient for broadband terahertz (THz) modulation with electrical and optical stimuli. However, the optimal protocol to apply optical and electrical stimuli has not been well-determined to obtain the best performance. Here, band theory of the hybrid diode has been used to analyze the underlying modulation mechanism and to help determine the optimal modulation protocol. Monolayer gold nanoparticles (AuNPs) were coated on the graphene/silicon hybrid diode to enhance the modulation performance. Both high modulation depth (similar to 93%) and modulation rate (similar to 4.6 kHz) were obtained with the AuNP-coated hybrid diode using the proper modulation method. To explore the underlying mechanism for a graphene/silicon hybrid diode THz modulator, this work could throw light on other material systems for THz modulation.