Wafer-Scale Synthesis of WS 2 Films with In Situ Controllable p-Type Doping by Atomic Layer Deposition.

Wafer-scale synthesis of p-type TMD films is critical for its commercialization in next-generation electro/optoelectronics. In this work, wafer-scale intrinsic n-type WS 2 films and in situ Nb-doped p-type WS 2 films were synthesized through atomic layer deposition (ALD) on 8-inch α -Al 2 O 3 /Si wafers, 2-inch sapphire, and 1 cm 2 GaN substrate pieces. The Nb doping concentration was precisely controlled by altering cycle number of Nb precursor and activated by postannealing. WS 2 n-FETs and Nb-doped p-FETs with different Nb concentrations have been fabricated using CMOS-compatible processes. X-ray photoelectron spectroscopy, Raman spectroscopy, and Hall measurements confirmed the effective substitutional doping with Nb. The on/off ratio and electron mobility of WS 2 n-FET are as high as 10 5 and 6.85 cm 2  V -1  s -1 , respectively. In WS 2 p-FET with 15-cycle Nb doping, the on/off ratio and hole mobility are 10 and 0.016 cm 2  V -1  s -1 , respectively. The p-n structure based on n- and p- type WS 2 films was proved with a 10 4 rectifying ratio. The realization of controllable in situ Nb-doped WS 2 films paved a way for fabricating wafer-scale complementary WS 2 FETs.