Charge Transfer at the Hetero‐Interface of WSe₂/InSe Induces Efficient Doping to Achieve Multi‐Functional Lateral Homo‐Junctions

Abstract

Charge transfer at the hetero‐interface is at the center of van der Waals (vdWs) heterostructure devices for multi‐functional applications. Compared with the extensively investigated photogenerated carrier transfer driven by the built‐in electric field from the conduction or valence band offset, the charge transfer due to the Fermi level difference of the two adjacent constitutes, and its influence on the opto‐/electronic performance of vdWs heterostructure devices are not clarified. Herein, by taking an example of WSe2/InSe heterostructure, it is demonstrated that the charge transfer at the hetero‐interface is an efficient “doping” strategy to dramatically modulate the carrier densities of atomically thin counterparts due to the extension of “band bending” across the entire heterostructure, paving the way for the creation of lateral WSe2 p‐n and n‐n+ homo‐junctions with multi‐functionalities, including promising rectification, photovoltaic, and photodetection abilities. Moreover, the device physics of lateral homo‐junctions, including potential distribution, band diagram, and photocurrent generation mechanisms, is revealed by gate‐dependent Kelvin probe force microscopy and scanning photocurrent measurements. This work not only provides a general avenue to build 2D lateral homo‐junctions, but also give deeper insights into the device physics of the junctions by coupling scanning probe and scanning photocurrent techniques.

Lateral layered semiconductor multijunctions for novel electronic devices

“…Recently, Xu et al used InSe as a substrate for carrier transfer in WSe 2 /InSe to form an n-doped WSe 2 region, which together with the connected primitive WSe 2 formed a substrate-modulated homojunction with a maximum rectification ratio of up to 1.5 Â 10 3 . 99 Another effective way to surface dope monolayer TMD is by charge transfer. The dopant can be gas molecules, 38 organic molecules 41 and atoms.…”

“…Recently, Xu et al used InSe as a substrate for carrier transfer in WSe 2 /InSe to form an n-doped WSe 2 region, which together with the connected primitive WSe 2 formed a substrate-modulated homojunction with a maximum rectification ratio of up to 1.5 × 10 3 . 99…”

Transistors and logic circuits enabled by 2D transition metal dichalcogenides: a state-of-the-art survey

“…However, when n-type dopants are added, the PL intensity decreases because the adsorption of the n-type dopant causes the PL emission to switch from excitons to charged excitons. 47,48 Impurity diffusion or ion insertion can accurately regulate the doping in typical semiconductors, but given that 2D semiconductor materials have no dangling bonds and possess atomic-level thickness, novel doping strategies must be devised. 49,50 Kim et al 51 utilized three p-type molecular dopants in their study, i.e., 2,3,5,6-tetra-fluoro-7,7,8,8-tetracyanoquinodimethane (F4-TCNQ), tris(4-bromophenyl)ammoniumyl hexachloroantimonate (magic blue), and molybdenum tris(1,2-bis(trifluoromethyl)ethane-1,2-dithiolene) (Mo(tfd-COCF 3 ) 3 ).…”

Coupling between Pyroelectricity and Built-In Electric Field Enabled Highly Sensitive Infrared Phototransistor Based on InSe/WSe2/P(VDF-TrFE) Heterostructure

“…Although there are few reports on ferroelectric gated 2D material transistors, there have been no studies on a pyroelectric gated 2D heterostructure. Here, we chose the type II InSe/WSe 2 heterostructure for our study, and there are limited reports on InSe-based heterostructures. , InSe is an n-type semiconductor with a band gap of 1.27 eV for a thickness of more than 6 nm and an electron mobility of 10 3 cm 2 /(Vs), whereas WSe 2 is a p-type semiconductor with a direct and indirect optical transition based on the number of layers and has a carrier mobility of 10 2 cm 2 /(Vs). − The InSe/WSe 2 heterostructure top-gated with P­(VDF-TrFE) dielectric shows an ambipolar transfer behavior, and the ferroelectric polarization results in a relatively higher photoresponsivity (λ = 633 nm) in the polarized state (10 4 A W –1 ) than the unpolarized state. During IR irradiation (λ = 980, 1064 nm) in the polarized state, due to the pyroelectric effect in P­(VDF-TrFE), a significant change in current was observed for different laser power intensities, which is indicative of the enhanced IR detection.…”

“…Here, we chose the type II InSe/WSe 2 heterostructure for our study, and there are limited reports on InSe-based heterostructures. 20,21 InSe is an n-type semiconductor with a band gap of 1.27 eV for a thickness of more than 6 nm and an electron mobility of 10 3 cm 2 /(Vs), whereas WSe 2 is a p-type semiconductor with a direct and indirect optical transition based on the number of layers and has a carrier mobility of 10 2 cm 2 /(Vs). 22−25 The InSe/WSe 2 heterostructure top-gated with P(VDF-TrFE) dielectric shows an ambipolar transfer behavior, and the ferroelectric polarization results in a relatively higher photoresponsivity (λ = 633 nm) in the polarized state (10 4 A W −1 ) than the unpolarized state.…”