Van der Waals junction field effect transistors with both n- and p-channel transition metal dichalcogenides

Hyung Gon Shin,Sanghyuck Yu,Yeonjin Yi,Taekyeong Kim,Kyeong Rok Ko,Seongil Im,Minju Kim,Yeonsu Jeong,June Yeong Lim,Jae Young Moon,Young Jai Choi

doi:10.1038/s41699-018-0082-2

Abstract

Two-dimensional (2D) transition metal dichalcogenides (TMDs)-based van der Waals (vdW) PN junctions have been used for heterojunction diodes, which basically utilize out-of-plane current across the junction interface. In fact, the same vdW PN junction structure can be utilized for another important device application, junction field effect transistors (JFETs), where in-plane current is possible along with 2D–2D heterojunction interface. Moreover, the 2D TMD-based JFET can use both p- and n-channel for low voltage operation, which might be its unique feature. Here we report vdW JFETs as an in-plane current device with heterojunction between semiconducting p- and n-TMDs. Since this vdW JFET would have low-density traps at the vdW interface unlike 2D TMD-based metal insulator semiconductor field effect transistors (MISFETs), little hysteresis of 0.0–0.1 V and best subthreshold swing of ~100 mV/dec were achieved. Easy saturation was observed either from n-channel or p-channel JFET as another advantage over 2D MISFETs, exhibiting early pinch-off at ~1 V. Operational gate voltage for threshold was near 0 V and our highest mobility reaches to ~>500 cm2/V·s for n-channel JFET with MoS2 channel. For 1 V JFET operation, our best ON/OFF current ratio was observed to be ~104.

Highlights

The same van der Waals (vdW) PN junction structure can be utilized for another important device application, junction field effect transistors (JFETs), where in-plane current is possible along with 2D–2D heterojunction interface
Blue and skyblue lines indicate the saturation mobility and black stars indicate the linear mobility at different VGS (−0.2, −0.4, −0.6, −0.8 V, respectively) linear mobilities (4 cm2/V·s) of p-channel JFET appear comparable to the previous reports from p-MoTe2 MISFETs25 but much inferior to the values from MoS2 JFET
Since this vdW JFET would have lowdensity traps at the vdW interface when p-type material plays as a gate for n-channel and vice versa, little hysteresis of 0.05–0.1 V and good subthreshold swing (SS) of ~100 mV/dec were achieved

Summary

Introduction

Two-dimensional (2D) transition metal dichalcogenides (TMDs) have been extensively studied in both aspects of materials and devices for the past decade, since those are regarded to have great potentials for future nanoelectronics.[1,2,3,4,5,6,7,8,9,10,11] Main focus has been on 2D TMD semiconductor devices, which are probably the most important for existing or future technologies.[3,8,9,10,11,12] Many of metal insulator semiconductor field effect transistors (MISFETs) using 2D TMD channels have been reported,[8,10,13,14,15,16,17,18,19,20,21,22] along with their use for complementary metal-oxide-semiconductor transistor inverters.[23,24,25,26,27,28] Heterojunction 2D TMD p–n (PN) diodes with van der Waals (vdW) interface have received much attention from researchers.[29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44] These vdW PN junction interfaces basically experience out-of-plane or vertical current across the junction during device operation.

Results

Conclusion