Understanding tunable photoresponsivity of two-dimensional multilayer phototransistors: Interplay between thickness and carrier mobility

Abstract

Thickness-dependent bandgap and carrier mobility of two-dimensional (2D) van der Waals (vdW) layered materials make them a promising material as a phototransistor that detects light signals and converts them to electrical signals. Thus far, to achieve a high photoresponsivity of 2D materials, enormous efforts have been made via material and dielectric engineering, as well as modifying device structure. Nevertheless, understanding the effect of interplay between the thickness and the carrier mobility to photoresponsivity is little known. Here, we demonstrate the tunable photoresponsivity (R) of 2D multilayer rhenium disulfide (ReS2), which is an attractive candidate for photodetection among 2D vdW materials owing to its layer-independent direct bandgap and decoupled vdW interaction. The gate bias (VG)-dependent photocurrent generation mechanism and R are presented for the channel thickness range of 1.7–27.5 nm. The high similarity between VG-dependent photocurrent and transconductance features in the ReS2 phototransistors clearly implies the importance of the channel thickness and the operating VG bias condition. Finally, the maximum R was found to be 4.1 × 105 A/W at 14.3 nm with the highest carrier mobility of ∼15.7 cm2⋅V−1⋅s−1 among the fabricated devices after excluding the contact resistance effect. This work sheds light on the strategy of how to obtain the highest R in 2D vdW-based phototransistors.

Restricted Channel Migration in 2D Multilayer ReS2

“…Such an anomalous carrier mobility enhancement along the thickness (up to 10 nm) at the given V BG and V D conditions for the i th layer of a 2D multilayer system can mainly be ascribed to the presence of fixed oxide charges inside the dielectrics and charged Coulomb impurities on the bottom and/or top surfaces of the 2D materials, in addition to an interlayer resistance and the effects of the Thomas-Fermi screening. 13,16,25,26 The thickness-dependent carrier mobility of multilayer ReS 2 is presented elsewhere, including our previous report. 16,27 The ThomasFermi charge screening length…”

“…13,16,25,26 The thickness-dependent carrier mobility of multilayer ReS 2 is presented elsewhere, including our previous report. 16,27 The ThomasFermi charge screening length…”

“…3,21,22 For example, Das et al systematically reported a non-monotonic thickness-dependent carrier mobility with respect to different metal electrodes ascribing to the ThomasFermi charge screening and interlayer coupling in MoS 2 multilayers. 19,20 In addition, Shim and Moon et al investigated systematically the thickness-dependent optoelectronic properties of ReS 2 thin film transistors, 14,16 and Lee and Kim et al probed the effects of interlayer tunneling barrier effects on the current fluctuation in a multilayer ReS 2 transistor with respect to the top and bottom surfaces. 3,21 Furthermore, Goyal et al demonstrated a feasible memory application using few-layer ReS 2 transistors upon the observance of two plateaus in its transconductance curves.…”

Modeling and Understanding the Compact Performance of h‐BN Dual‐Gated ReS2 Transistor

“…[1] Transition-metal dichalcogenide (TMD) materials are promising candidates to replace the Si channel because of their high carrier mobility, excellent applicability, mechanical, optical, and electrical properties. [2][3][4][5][6][7][8][9][10] Among these numerous TMD materials, rhenium disulfide (ReS 2 ) has a distorted 1T structure [11] with higher interlayer resistance (R int ) compared to other TMD materials, [12,13] and anisotropic electrical and optical properties. [13,14] Recently, in comparison with the well-known molybdenum disulfide (MoS 2 ), which has the 2H phase, ReS 2 has attracted significant attention because of its direct bandgap from single layer to bulk since each layer is decoupled from the other.…”

Cyclic Thermal Effects on Devices of Two‐Dimensional Layered Semiconducting Materials

“…Nano‐electronic devices based on transition‐metal dichalcogenides (TMD) materials, which have high carrier mobility, excellent electrical property, and optical property, have been widely considered for next generation nano‐electronic applications. [ 1–8 ] In comparison with conventional silicon‐based devices, field‐effect transistors (FETs) based on TMD materials as a channel have advantages of large surface area, ultrathin channel thickness, and excellent surface stability. [ 9–11 ] Recently, TMD devices having a 3D structure beyond a planar structure, and TMD circuits fabricated by wafer‐level processes have been widely studied.…”