Gate-Tunable Tunneling Transistor Based on a Thin Black Phosphorus–SnSe₂ Heterostructure

Abstract

Tunneling field-effect transistors (TFETs) are of considerable interest owing to their capability of low-power operation. Here, we demonstrate a novel type of TFET which is composed of a thin black phosphorus–tin diselenide (BP–SnSe2) heterostructure. This combination of 2D semiconductor thin sheets enables device operation either as an Esaki diode featuring negative differential resistance (NDR) in the negative gate voltage regime or as a backward diode in the positive gate bias regime. Such tuning possibility is imparted by the fact that only the carrier concentration in the BP component can be effectively modulated by electrostatic gating, while the relatively high carrier concentration in the SnSe2 sheet renders it insensitive against gating. Scanning photocurrent microscopy maps indicate the presence of a staggered (type II) band alignment at the heterojunction. The temperature-dependent NDR behavior of the devices is explainable by an additional series resistance contribution from the individual BP and SnSe2 sheets connected in series. Moreover, the backward rectification behavior can be consistently described by the thermionic emission theory, pointing toward the gating-induced formation of a potential barrier at the heterojunction. It furthermore turned out that for effective Esaki diode operation, care has to be taken to avoid the formation of positive charges trapped in the alumina passivation layer.

Tunable Electronic and Optical Properties of 2D Monoelemental Materials Beyond Graphene for Promising Applications

“…Although 2D materials have various carrier densities and electron affinities, constructing a heterojunction can be used for band alignment design to meet the requirements of tunnel field-effect transistors and can also effectively improve the instability of BP, so Liu et al [249] studied BP/MoS 2 heterojunction and found that the thickness of BP layer largely determines the junction characteristics and actually adjusts the doping level of BP flakes. In another work, Na et al [250] fabricated p-BP/n-SnSe 2 heterostructure and a novel vertical BP/SnSe 2 tunnel field-effect transistor (TFET) to effectively separate electron-hole pairs.…”

Intrinsic Electronic Transport Properties and Carrier Densities in PtS2 and SnSe2: Exploration of n+‐Source for 2D Tunnel FETs

“…Indeed, only intrinsic n + -SnSe 2 is utilized for the source. [18][19][20][21][22][23] Although there are some reports on p-type 2D-TFETs with nondegenerately doped source materials, [24][25][26][27] electrostatic doping by an additional local gate electrode has been applied to the sources, which causes other problems, such as a complicated device structure and an increase in the parasitic capacitance. Recently, the substitutional doping technique during 2D growth has been intensively investigated.…”

Recent progress and challenges on two-dimensional material photodetectors from the perspective of advanced characterization technologies

“…During the procedure, contaminants and air gaps are introduced at the interface, unintentionally. The imperfect interface induces additional trap states and tunneling barriers, which introduces an additional resistance [100,101]. Gao et al fabricated a vertical InSe/bP heterostructures with a high-quality interface [102].…”