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HL: Fachverband Halbleiterphysik

HL 47: 2D Materials: Heterostuctures

HL 47.1: Talk

Thursday, March 21, 2024, 15:00–15:15, EW 201

Controlled Encapsulation of Monolayer MoS₂ with Ultrathin Aluminum Oxide for Tunnel Contacts — •Sergej Levashov, Chenjiang Qian, Theresa Grünleitner, Jon J. Finley, Alex Henning, and Ian D. Sharp — Walter Schottky Institut and TUM School of Natural Sciences, Technische Universität München

Two-dimensional (2D) semiconductors have unique optoelectronic properties that provide the opportunity to overcome current scaling and performance limits of semiconductor devices. Harnessing the full potential of 2D materials requires their seamless integration with bulk materials, which is challenging for mono- and few-layer 2D materials since the deposition process may introduce defects, thereby impeding interfacial charge transport. Here, we use low-temperature atomic layer deposition (ALD) to encapsulate monolayer MoS₂ with a van der Waals bonded and ultrathin aluminium oxide (AlO_x) layer. The weakly bonded 18 Å thin AlO_x coating introduces additional charge carriers (∼4×10¹² cm⁻²) while it also protects monolayer MoS₂ from defect creation during metallization. Moreover, an AlO_x thickness dependent study revealed an interface-dominated change in excitonic features. Fabricated field-effect transistors (FETs) show an additional charge transfer doping of up to ∼8.5×10¹²cm⁻² due to trap state relaxation after inert gas annealing and, more importantly, a five-fold reduction in the contact resistance for MoS₂ FETs contacted with an AlO_x interlayer. Overall, this work shows the beneficial effect of the ALD AlO_x adlayer for improving 2D device contacts and provides a scalable route to the damage-free integration of 2D semiconductors.