Reversible Charge‐Polarity Control for Multioperation‐Mode Transistors Based on van der Waals Heterostructures

Abstract

Van der Waals (vdW) heterostructures-in which layered materials are purposely selected to assemble with each other-allow unusual properties and different phenomena to be combined and multifunctional electronics to be created, opening a new chapter for the spread of internet-of-things applications. Here, an O 2 -ultrasensitive MoTe 2 material and an O 2 -insensitive SnS 2 material are integrated to form a vdW heterostructure, allowing the realization of charge-polarity control for multioperation-mode transistors through a simple and effective rapid thermal annealing strategy under dry-air and vacuum conditions. The charge-polarity control (i.e., doping and de-doping processes), which arises owing to the interaction between O 2 adsorption/desorption and tellurium defects at the MoTe 2 surface, means that the MoTe 2 /SnS 2 heterostructure transistors can reversibly change between unipolar, ambipolar, and anti-ambipolar transfer characteristics. Based on the dynamic control of the charge-polarity properties, an inverter, output polarity controllable amplifier, p-n diode, and ternary-state logics (NMIN and NMAX gates) are demonstrated, which inspire the development of reversibly multifunctional devices and indicates the potential of 2D materials.

Reversible charge-polarity control for a photo-triggered anti-ambipolar In2Se3&WSe2 heterotransistor

“…Among them, the most prominent is the anti-ambipolar behavior, which offers great advantages in the application in emerging circuits, for example, in the simultaneous phase, amplitude shift keying, and frequency doubling circuits for wireless communication technologies. 6–11 Anti-ambipolar behavior, which was first observed in carbon nanotubes and MoS 2 in 2013, 12 can be thought of as arising from a field effect transistor (FET) channel consisting of P-type and N-type semiconductors connected in series. It exhibits an inverted V-shaped transport characteristic in which the channel conductance peaks at a specific gate bias, especially, several anti-ambipolar vdWHs with the capability of possessing both positive and negative transconductance, which are promising for the realization of more functions with a lower number of devices.…”

Defect Engineering of MoTe2 via Thiol Treatment for Type III van der Waals Heterojunction Phototransistor

“…SnS 2 , with a substantial electron affinity around 5.2 eV, maintains an n-type polarity, which is critical for forming type III band alignment with many other p-type TMD materials, which may be of interest for next generation tunneling FETs. , While a MoTe 2 /SnS 2 JFET was successfully fabricated by Kim et al in 2020, the device exhibited only strong electron polarities . To address this challenge, Chen et al achieved control over the charge polarity of the MoTe 2 /SnS 2 JFET through the surface adsorption of oxygen containing molecules . However, the weak physical interaction between oxygen and MoTe 2 can result in unstable operation in ambient air. , Although the above discussion underscores the growing interest in reliable p-doping methods for MoTe 2 and its practical applications, reports on BTBT in p-MoTe 2 /n-SnS 2 type III heterojunctions remain scarce due to the low hole concentration in MoTe 2 .…”

“…To address this challenge, Chen et al achieved control over the charge polarity of the MoTe 2 /SnS 2 JFET through the surface adsorption of oxygen containing molecules . However, the weak physical interaction between oxygen and MoTe 2 can result in unstable operation in ambient air. , Although the above discussion underscores the growing interest in reliable p-doping methods for MoTe 2 and its practical applications, reports on BTBT in p-MoTe 2 /n-SnS 2 type III heterojunctions remain scarce due to the low hole concentration in MoTe 2 . Developing a robust and effective p-type doping method for MoTe 2 is expected to provide an additional p-type TMD material, complementing the existing research focused on WSe 2 -based type III heterojunction studies. , …”

2D van der Waals Vertical Heterojunction Transistors for Ternary Neural Networks

“…Two-dimensional (2D) materials offer competitive opportunities to design new device architectures for TNN circuits through heterogeneous integration, showing the potential for ternary functions within a single device. Currently, 2D heterojunction transistors (HTRs) with a negative differential transconductance (NDT) region, where the channel transconductance shifts steeply from positive to negative with increasing gate voltage, have been used to design ternary inverters. − But the negative differential transconductance region in NDT-HTRs cannot form relatively flat intermediate conductance states, − making them difficult to perform the quantization function of TNN. Therefore, developing ternary devices suitable for TNN is still a challenge.…”

“…As the input voltage is V in < −7 V, the output voltage is low (∼0.1 V); when the input voltage is V in > 14 V, the output voltage is high (∼5.7 V); otherwise, the output voltage is intermediate (∼1.8 V). The 2D V-HTR exhibited the quantization function and showed a complete ternary ADC remains to be explored, including sampling, holding, quantization, and encoding circuits. − On the other hand, the ternary transistors provide a compact structure to realize a balanced standard ternary inverter (BSTI) by connecting in series with a 2 GΩ resistor, as shown in Figure e. The input and output characteristics under different V dd are shown in Figure f.…”