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

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 E-2g(1) 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 cm(2) V-1 s(-1) at room temperature. The on/off ratio of the output current is similar to 10(8) at room temperature. The mobility of a multilayer ML-WS2 FET was found to be 425 cm(2) 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.