Wafer-Scale Synthesis of WS2 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 WS2 films and in situ Nb-doped p-type WS2 films were synthesized through atomic layer deposition (ALD) on 8-inch alpha-Al2O3/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. WS2 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 WS2 n-FET are as high as 10(5) and 6.85 cm(2) V-1 s(-1), respectively. In WS2 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 WS2 films was proved with a 10(4) rectifying ratio. The realization of controllable in situ Nb-doped WS2 films paved a way for fabricating wafer-scale complementary WS2 FETs.

Automated summary

Wafer-scale synthesis of intrinsic n-type and in situ Nb-doped p-type WS2 films were achieved through atomic layer deposition on various substrates. The fabricated WS2 FETs exhibited high on/off ratio and electron or hole mobility, confirming the effectiveness of Nb doping and the potential for wafer-scale complementary WS2 FETs.