Normally off WSe₂Nanosheet-Based Field-Effect Transistors with Self-Aligned Contact Doping

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 WSe₂semiconductor FET by forming the lateral p-n homojunction. The self-aligned n-doping of the ambipolar WSe₂was obtained by intentionally forming Se vacancy via mild Ar-ion treatment. The UV-ozone-assisted growth of the WO_Xlayer increased the hole concentrations of the WSe₂channel, where its high work function makes the underlying WSe₂electron-deficient. A high on/off ratio of ∼10⁸and a wide off-range gate bias with the normally off operation were obtained in the n-p-n nanostructured WSe₂FETs, 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 °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 nanosheet-based WSe₂FET 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.