Energy-efficient tunnel field-effect transistors and twistronics based on 2D materials

Abstract

however, so far they have not achieved the essential criteria for fast, low-power switches. Here, we report a Heterojunction (HJ)-TFET with spatially varying layer thickness in black phosphorus (BP) without interface problems. We use bulk and monolayer BP as the source and channel of the HJ-TFETs, respectively, to take advantage of unique BP band properties to solve the interface problem which degrades performance for HJ-TFETs. We achieve record-low average subthreshold swing (SS) values SS$_{ave_4dec}$ ≈ 23.7 mV/dec with high I$_{60}$ = 0.65–1 μA/μm. Additionally, we report complementary trilayer-bulk BP HJ-TFETs with an SS$_{min}$ of 17.7 mV/dec (21.3 mV/dec) for p-type (n-type) operation. In the same devices, SS > 60 mV/dec is exhibited when BTBT occurs within the trilayer BP, indicating that BTBT between the heterojunction of a trilayer-bulk BP is the key to achieving a sub-thermionic SS. More recently, it was revealed that twisting two dimensional van der Waals materials with small angle can creates moiré pattern resulting in novel electronic phenomena. For instance, twisted bilayer graphene (TBG) with θ ≈ 1.1° exhibits correlated insulating states at partial fillings of flat bands and reveals superconductivity and ferromagnetism near such fillings. In this research, we twist the monolayer-bilayer graphene and measure the electronic properties at low temperature and find the signature of superconductivity and ferromagnetism. Additionally, we apply compressive strain to TBG device and observe the resistance peak splitting and dip emerging near three-half fillings (3n$_s$/2 peaks). Finally, we fabricate twisted MoS$_2$ bilayer device and obtain the new insulating states at low temperature which were never seen in monolayer device before.

Transistor downscaling by Moore’s law has facilitated drastic improvements in information technology, however, as transistors decrease in size, quantum tunneling causes increased leakage currents and power consumption. Tunnel field-effect transistors (TFETs) have been suggested to address these issues