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Title: Engineering of Interface Barrier in Hybrid MXene/GaN Heterostructures for Schottky Diode Applications

Authors: D. Majchrzak, K. Kulinowski, W. Olszewski, R. Kuna, D. Hlushchenko, A. Piejko, M. Grodzicki, D. Hommel, R. Kudrawiec

Journal: ACS Applied Materials & Interfaces

DOI: 10.1021/acsami.4c13225   

The paper reports the study of the engineering of interface barriers in hybrid MXene/GaN heterostructures intended for Schottky diode applications. For the first time, contactless electroreflectance (CER) spectroscopy was applied to analyze the built-in electric fields in MXene/GaN heterostructures involving five different MXenes (Cr₂C, Mo₂C, V₂C, V₄C₃, Ti₃C₂). It was found that MXene deposition shifts the Fermi level, thus increasing the barrier height at the MXene/GaN interface. These interface barriers were also studied post-annealing at 750°C, demonstrating enhanced stability and increased barrier heights. To practically demonstrate the concept, Schottky diodes with the highest barrier height MXenes (Mo₂C and V₂C) were fabricated, resulting in improved diode performance, notably reduced leakage currents and increased forward voltages.

Xene/GaN heterostructures were studied using contactless electroreflectance (CER) to determine the built-in electric field at MXene/GaN interfaces and x-ray photoelectron spectroscopy (XPS) to analyze the physicochemical properties of MXene/GaN structures, ultraviolet photoelectron spectroscopy (UPS) – for determining ionization energies and work functions, scanning electron microscopy (SEM) – for analyzing surface morphology after treatment and annealing and Current–Voltage (I–V) measurements – to characterize electrical performance of fabricated MXene/GaN Schottky diodes.

The studies' originality are:

• utilization CER (contactless electroreflectance) to study built-in electric fields in MXene/GaN heterostructures.
• experimental determination of barrier heights at MXene/GaN interfaces.
• demonstration of MXene stability on GaN even after high-temperature annealing.
• practical validation by fabricating MXene/GaN Schottky diodes with optimized barrier heights.