A high-frequency silicon-graphene-germanium barristor

Realising ubiquitous environmental monitoring and smart sensing devices compatible with Internet of Things (IoT) and 6 G networks requires transistors with terahertz (THz) cutoff frequencies (f_T) for efficient signal processing. However, the carrier transit time intrinsically limits conventional devices. Vertical two-dimensional (2D) base transistors offer a way to exceed this limit, yet interface losses typically suppress current gain, degrade high-frequency performance, and hinder THz operation. Here, we report a silicon–graphene–germanium barristor that overcomes these obstacles. Wafer-scale single-crystal graphene was epitaxially grown on germanium and integrated with silicon membranes, forming asymmetric Schottky barriers at the graphene–silicon and graphene–germanium interfaces. Using graphene’s quantum capacitance, the asymmetric barriers enable distinct hot-carrier emission at both terminals and greatly increase the current gain, while graphene’s atomic thickness minimises the perpendicular transit time. As a result, the device achieves a current gain up to 1.8 × 10⁷ and an intrinsic f_T up to 132 GHz, with modelling and simulation indicating scalability into the THz regime. These findings establish a promising high-frequency transistor paradigm for IoT sensors and systems.