High current density heterojunction bipolar transistors with 3D-GaN/2D-WSe₂ as emitter junctions

With the continuous advancement of electronic technology, there is an increasing demand for high-speed, high-frequency, and high-power devices. Due to the inherently small thickness and absence of dangling bonds of two-dimensional (2D) materials, heterojunction bipolar transistors (HBTs) based on 2D layered materials (2DLMs) have attracted significant attention. However, the low current density and limited structural design flexibility of 2DLM-based HBT devices currently hinder their applications. In this work, we present a novel vertical GaN/WSe₂/MoS₂ HBT with three-dimensional (3D)-GaN/2D-WSe₂ as the emitter junction. Harnessing the high carrier concentration and wide bandgap of 3D-GaN, an HBT with a current density of about 260 A cm^-2 is obtained. In addition, by selecting an adequate position for the collector electrode, we achieve efficient carrier collection through a collector junction smaller than the emitter junction area, obtaining a common-base current gain of 0.996 and a remarkable common-emitter current gain (β) of 12.4.