All 2D Heterostructure Tunnel Field-Effect Transistors: Impact of Band Alignment and Heterointerface Quality

Van der Waals heterostructures are the ideal material platform for tunnel field-effect transistors (TFETs) because a band-to-band tunneling (BTBT) dominant current is feasible at room temperature (RT) because of ideal, dangling bond-free heterointerfaces. However, achieving subthreshold swing (SS) values lower than 60 mV dec^-1 of the Boltzmann limit is still challenging. In this work, we systematically studied the band alignment and heterointerface quality in n-MoS₂ channel heterostructure TFETs. By selecting a p⁺-MoS₂ source with a sufficiently high doping level, stable gate modulation to a type III band alignment was achieved regardless of the number of MoS₂ channel layers. For the gate stack formation, it was found that the deposition of Al₂O₃ as the top gate introduces defect states for the generation current under reverse bias, while the integration of a hexagonal boron nitride (h-BN) top gate provides a defect-free, clean interface, resulting in the BTBT dominant current even at RT. All 2D heterostructure TFETs produced by combining the type III n-MoS₂/p⁺-MoS₂ heterostructure with the h-BN top-gate insulator resulted in low SS values at RT.