Ambipolar‐To‐Unipolar Conversion in Ultrathin 2D Semiconductors

Abstract

Achieving the full potential of any semiconductor device needs an understanding and precise control of carrier transport behavior, which significantly affects the stability and power consumption in future large‐scale integrated circuits. Compared to other semiconductor materials, bipolar 2D semiconductor materials often face difficulty in turning off channel currents, which seriously challenges the development of low‐power semiconductor devices. Here, a review of the studies on transforming ambipolar conduction in 2D materials to get unipolar p‐type/n‐type semiconductors is presented. In particular, 2D semiconductors of black phosphorus and transition metal dichalcogenides such as WSe2 and MoTe2 are investigated. The intrinsic and extrinsic factors that can directly affect the behavior of carriers, such as contact engineering, chemical doping, surface charge transfer doping, electrostatic gating, and dielectric engineering, are focused. Furthermore, how these ambipolar‐to‐unipolar conversion strategies can be applied to tune device performance and construct new‐structure electronic and optoelectronic devices are showcased. Finally, the most critical challenges and future developments in ambipolar‐to‐unipolar conversion engineering in 2D materials are summarized.

Controllable Modulation of the Electronic Properties of a Two-Dimensional Ambipolar Semiconductor by Interface Ferroelectric Polarization

“…Ambipolar semiconductors, given their unique ability to reversibly tune the primary charge carriers between holes and electrons simply by applied external gate bias, have attracted significant attention. This is because electrons and holes can transport concurrently in ambipolar semiconductors that enable the integration of p- and n-type electrical conductivity into a single device. − Among them, two-dimensional (2D) ambipolar semiconductors exhibit excellent ambipolar characteristics, as they can efficiently avoid the electric screening effect in the presence of gate bias. The quantum confinement effect in 2D ambipolar semiconductors results in low density of states in the electronic structures as compared to their bulk ambipolar counterparts, which allow for switching of types of primary charge carriers by low gate bias.…”

Recent progress on ambipolar 2D semiconductors in emergent reconfigurable electronics and optoelectronics

“…So far, the significance of ambipolar 2D semiconductors has been recognized with lots of significant advancements, and a few specialized reviews have been composed in this field. [34][35][36][37] Here we dedicate an overview on the recent progress of ambipolar 2D semiconductors applied in reconfigurable devices and circuits. We hope the review will help readers to well understand the applications of ambipolar 2D semiconductors, and push forward exploring newprinciple devices and new-architecture computing circuits, and even their product applications.…”

Controlled Synthesis of Ultrathin Cu2Te Nanosheets for High-Performance Photodetectors

“…Since the discovery of graphene, more and more two-dimensional (2D) materials such as 2D transition metal dichalcogenides (TMDs) as one of the research hotspots are emerging, which typically feature unconventional physical and chemical properties including atomic-level thickness, diverse crystal structures, and layer-dependent band gap, and such research works have made great advances in electronics, optoelectronics, magnetism, and energy. − The library of related 2D semiconducting materials therefore has been continuously expanding, especially n-type semiconductors, and the n-type semiconductor behavior is always caused by the strong electron doping from interfacial charge impurities and intrinsic structural defects. , Represented n-type semiconductors with high electron mobility and environmental stability are MoS 2 , Bi 2 O 2 Se, etc. In contrast, natural p-type 2D semiconductors with holes as majority carriers are still scarce.…”