Normally Off WSe2 Nanosheet-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 WSe 2 semiconductor FET by forming the lateral p–n homojunction. The self-aligned n-doping of the ambipolar WSe 2 was obtained by intentionally forming Se vacancy via mild Ar-ion treatment. The UV-ozone-assisted growth of the WO X layer increased the hole concentrations of the WSe 2 channel, where its high work function makes the underlying WSe 2 electron-deficient. A high on/off ratio of ∼10 8 and a wide off-range gate bias with the normally off operation were obtained in the n–p–n nanostructured WSe 2 FETs, which was also characterized by photocurrent mapping analysis. The electrical characteristics of the devices exhibited their thermal…