Enhanced transport in transistor by tuning transition-metal oxide electronic states interfaced with diamond

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Science Advances  28 Sep 2018:
Vol. 4, no. 9, eaau0480
DOI: 10.1126/sciadv.aau0480


High electron affinity transition-metal oxides (TMOs) have gained a central role in two-dimensional (2D) electronics by enabling unprecedented surface charge doping efficiency in numerous exotic 2D solid-state semiconductors. Among them, diamond-based 2D electronics are entering a new era by using TMOs as surface acceptors instead of previous molecular-like unstable acceptors. Similarly, surface-doped diamond with TMOs has recently yielded record sheet hole concentrations (2 × 1014 cm−2) and launched the quest for its implementation in microelectronic devices. Regrettably, field-effect transistor operation based on this surface doping has been so far disappointing due to fundamental material obstacles such as (i) carrier scattering induced by nonhomogeneous morphology of TMO surface acceptor layer, (ii) stoichiometry changes caused by typical transistor fabrication process, and (iii) carrier transport loss due to electronic band energy misalignment. This work proposes and demonstrates a general strategy that synergistically surmounts these three barriers by developing an atomic layer deposition of a hydrogenated MoO3 layer as a novel efficient surface charge acceptor for transistors. It shows high surface uniformity, enhanced immunity to harsh fabrication conditions, and benefits from tunable electronic gap states for improving carrier transfer at interfaces. These breakthroughs permit crucial integration of TMO surface doping into transistor fabrication flows and allow outperforming electronic devices to be reached.

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