Room‐Temperature WSe₂ Impact Ionization Field‐Effect Transistor Based on a Stepwise Homojunction

The low subthreshold swing (SS) below the Boltzmann thermionic limitation (60 mV dec^-1) is crucial for the development of power-efficient transistors. Recently, impact ionization field-effect transistors (II-FETs), which leverage carrier avalanche multiplication, have emerged as an attractive method for achieving ultra-steep SS, high on-state current density, and significant drain current on-off ratio. However, current II-FETs face challenges due to complex fabrication processes, hindering the development of future array devices. In this work, a novel II-FET is reported based on a stepwise van der Waals WSe₂ homojunction. The device exhibits a low SS of 3.09 mV dec^-1 and a high multiplication factor exceeding 10⁴ at room temperature. Additionally, by lowering the operating temperature, the SS can be further improved to 0.25 mV dec^-1. Along with the improved subthreshold characteristics, the device shows a current on/off ratio >10⁵ and an on-state current density of ~1 µA µm^-1. The findings presented here offer a promising approach to developing energy-efficient electronic devices for future technological generations.