Normally Off WSe2 Nanosheet-Based Field-Effect Transistors with Self-Aligned Contact Doping

Abstract

Despite the advantages of ambipolar semiconductors, high off currents and narrow off-state bias window limit their application in enhancement mode field-effect transistors (FETs). We demonstrate the normally off operation of a low-dimensional ambipolar WSe2 semiconductor FET by forming the lateral p-n homojunction. The self-aligned n-doping of the ambipolar WSe2 was obtained by intentionally forming Se vacancy via mild Ar-ion treatment. The UV-ozone assisted growth of the WOX layer increased the hole concentrations of the WSe2 channel, where its high work function makes the underlying WSe2 electron deficient. A high on/off ratio of similar to 108 and a wide off-range gate bias with the normally off operation were obtained in the n-p-n nanostructured WSe2 FETs, which was also characterized by photocurrent mapping analysis. The electrical characteristics of the devices exhibited their thermal stability up to an operating temperature of 140 degrees C, which was enabled by the formation of the p-n homojunction barrier. High on/off ratios, wide off-range bias, and decent field-effect carrier mobility of the normally off nanosheetbased WSe2 FET were well maintained at elevated temperatures, which indicates that the low-dimensional ambipolar semiconductor with a junction barrier can play a pivotal role in the next-generation device architecture.