Tailoring the electrical and photo-electrical properties of a WS2 field effect transistor by selective n-type chemical doping

Abstract

Here, we demonstrate a doping technique which remarkably improves the electrical and photoelectric characteristics of a WS₂ field effect transistor (FET) by chemical doping. The shift of the threshold voltage towards a negative gate voltage and the red shift of the E¹_2g and A_1g peaks in the Raman spectra confirm the n-type doping effect in WS₂ FETs. WS₂ films show an unprecedented high mobility of 255 cm² V⁻¹ s⁻¹ at room temperature. The on/off ratio of the output current is ∼10⁸ at room temperature. The mobility of a multilayer ML-WS₂ FET was found to be 425 cm² V⁻¹ s⁻¹ at 5 K. Semiconductor-to-metal transitions were also observed at V_bg > 30 V. A decrease in contact and sheet resistance was observed after potassium iodide (KI) doping. The photocurrent in WS₂ FETs was also enhanced after n-type doping. Chemical doping exhibited a very stable, effective, and easy-to-apply method to enhance the performance of a WS₂ FET.