Role of layer thickness and field-effect mobility on photoresponsivity of indium selenide (InSe)-based phototransistors

Milinda Wasala,Saikat Talapatra,Sidong Lei,Prasanna Patil,Lincoln Weber,Sujoy Ghosh

doi:10.1093/oxfmat/itab010

Abstract

Abstract Understanding and optimizing the properties of photoactive two-dimensional (2D) Van der Waals solids is crucial for developing optoelectronics applications. The main goal of this work is to present a detailed investigation of layer dependent photoconductive behavior of indium selenide (InSe)-based field-effect transistors (FETs). InSe-based FETs with five different channel thicknesses (t, 20 nm &lt; t &lt; 100 nm) were investigated with a continuous laser source of λ = 658 nm (1.88 eV) over a wide range of illumination power (Peff) of 22.8 nW &lt; P &lt; 1.29 μW. All the devices studied showed signatures of photogating; however, our investigations suggest that the photoresponsivities are strongly dependent on the thickness of the conductive channel. A correlation between the field-effect mobility (µFE) values (as a function of channel thickness, t) and photoresponsivity (R) indicates that in general R increases with increasing µFE (decreasing t) and vice versa. Maximum responsivities of ∼7.84 A/W and ∼0.59 A/W were obtained the devices with t = 20 nm and t = 100 nm, respectively. These values could substantially increase under the application of a gate voltage. The structure–property correlation-based studies presented here indicate the possibility of tuning the optical properties of InSe-based photo-FETs for a variety of applications related to photodetector and/or active layers in solar cells.

Highlights

The advent of layered Van der Waals solids [1,2,3] and the envisioned applications that are being expected [4,5,6,7,8,9,10,11,12,13] have led to a large variety of fundamental as well as applied scientific investigations
The main goal of this work is to present a detailed investigation of layer dependent photoconductive behavior of indium selenide (InSe)-based field-effect transistors (FETs)
We found that room temperature responsivity at the lowest illumination power with voltage biases (VGS) 1⁄4 0 V and VDS 1⁄4 100 mV is $0.5 A/W

Summary

Introduction

The advent of layered Van der Waals solids [1,2,3] and the envisioned applications that are being expected [4,5,6,7,8,9,10,11,12,13] have led to a large variety of fundamental as well as applied scientific investigations. 2D layered semiconductors such as molybdenum disulfide (MoS2) are direct band gap materials in monolayer form but are indirect band materials in multilayer form, while materials such as indium selenide (InSe) have a direct band gap in multilayer form and an indirect band material in monolayer form. Such effects on intrinsic properties due to the simple addition of layers influence the functional properties of devices such as field-.

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