Wafer-Scale Synthesis of WS <sub>2</sub> Films with In Situ Controllable p-Type Doping by Atomic Layer Deposition
Hanjie Yang, Yang Wang, Xingli Zou, Rongxu Bai, Zecheng Wu, Sheng Han, Tao Chen, Shen Hu, Hao Zhu, Lin Chen, David W. Zhang, Jack C. Lee, Xionggang Lu, Peng Zhou, Qingqing Sun, Edward T. Yu, Deji Akinwande, Ji Li
Abstract
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.