Charge Transfer Doping of MoS₂ Field-Effect Transistors by Aluminum Oxynitride Deposition

This study demonstrates the n-type charge transfer doping of molybdenum disulfide (MoS₂) using aluminum oxynitride (AlON) overlayers. By optimizing the composition of AlON, electron doping is enhanced to 3.0 × 10¹² cm⁻², accompanied by a 43% improvement in field-effect mobility. The doping mechanism is systematically explored through detailed analyses of band alignment and oxygen-related in-gap state structures. Band alignment is investigated using X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy, while the in-gap states of AlON are characterized via spectroscopic ellipsometry. The doping efficiency is closely linked to Fermi level shifts and oxygen-related in-gap states in the AlON overlayers, which are effectively tuned by controlling the N₂ flow rate during sputter deposition. These findings establish AlON as a promising and adaptable material for doping 2D semiconductors, offering a tunable doping strategy via reactive gas flow control.