Atomic Layer Deposition of Al-Doped MoS₂: Synthesizing a p-type 2D Semiconductor with Tunable Carrier Density

Extrinsically doped two-dimensional (2D) semiconductors are essential for the fabrication of high-performance nanoelectronics among many other applications. Herein, we present a facile synthesis method for Al-doped MoS₂ via plasma-enhanced atomic layer deposition (ALD), resulting in a particularly sought-after p-type 2D material. Precise and accurate control over the carrier concentration was achieved over a wide range (10¹⁷ up to 10²¹ cm^-3) while retaining good crystallinity, mobility, and stoichiometry. This ALD-based approach also affords excellent control over the doping profile, as demonstrated by a combined transmission electron microscopy and energy-dispersive X-ray spectroscopy study. Sharp transitions in the Al concentration were realized and both doped and undoped materials had the characteristic 2D-layered nature. The fine control over the doping concentration, combined with the conformality and uniformity, and subnanometer thickness control inherent to ALD should ensure compatibility with large-scale fabrication. This makes Al:MoS₂ ALD of interest not only for nanoelectronics but also for photovoltaics and transition-metal dichalcogenide-based catalysts.