Ultra-Steep Slope Impact Ionization Transistors Based on Graphene/InAs Heterostructures

Abstract

With the continued scaling of transistors, there is a growing trend for developing steep slope transistors with subthreshold swing (SS) below Boltzmann limitation (kT/q). To this end, impact ionization metal oxide semiconductor (I-MOS) transistors are attractive for a unique combination of high ON-state current density, small hysteresis, and ultra-steep SS slope. However, the performance of I-MOS is generally limited by the relatively thick depletion region and large operation voltage required for the activation of impact ionization (typically >5 V). Herein, a high-performance I-MOS is constructed by van der Waals integrating single-crystal InAs film with graphene. Due to the low bandgap of InAs as well as the semi-metallic nature of graphene, the InAs/graphene I-MOS demonstrates a low operation voltage of 1.5 V, high ON-state current of 230 μA μm−1, steep SS <0.6 mV dec−1, and large ON–OFF ratio >106 at temperature below 200 K. Furthermore, a negative transconductance and steep current oscillation is observed in the subthreshold regime, and a device working mechanism is proposed for this novel phenomenon. This study not only pushes the performance limit of I-MOS but also defines a general pathway to van der Waals heterostructures between conventional III–V compound semiconductors and novel 2D materials for unconventional device functions.