Van der Waals interfaces in epitaxial vertical metal/2D/3D semiconductor heterojunctions of monolayer MoS 2 and GaN

• Published in: 2d materials Vol. 5; no. 4; p. 45016
• Main Authors: Ruzmetov, Dmitry, Neupane, Mahesh R, Herzing, Andrew, O'Regan, Terrance P, Mazzoni, Alex, Chin, Matthew L, Burke, Robert A, Crowne, Frank J, Birdwell, A Glen, Taylor, DeCarlos E, Kolmakov, Andrei, Zhang, Kehao, Robinson, Joshua A, Davydov, Albert V, Ivanov, Tony G
• Format: Journal Article
• Language: English
• Published: England 02.08.2018
• Subjects: contacts to 2D; p-GaN; molybdenum disulfide; 2D/3D heterojunctions; gallium nitride; TEM; Schottky barrier
• ISSN: 2053-1583; 2053-1583
• DOI: 10.1088/2053-1583/aad1b7

A promising approach for high speed and high power electronics is to integrate two-dimensional (2D) materials with conventional electronic components such as bulk (3D) semiconductors and metals. In this study we explore a basic integration step of inserting a single monolayer ( ) inside a -GaN junction and elucidate how it impacts the structural and electrical properties of the junction. Epitaxial in the form of 1-2 m triangle domains are grown by powder vaporization on a -doped GaN substrate, and the Au capping layer is deposited by evaporation. Transmission electron microscopy (TEM) of the van der Waals interface indicates that remained distinct and intact between the Au and GaN and that the Au is epitaxial to GaN only when the is present. Quantitative TEM analyses of the van der Waals interfaces are performed and yielded the atomic plane spacings in the heterojunction. Electrical characterization of the all-epitaxial, vertical / -GaN heterojunctions enables the derivations of Schottky barrier heights (SBH) and drawing of the band alignment diagram. Notably, appears to be electronically semi-transparent, and thus can be considered as a modifier to the Au contact rather than an independent semiconductor component forming a -junction. The analysis and our first principles calculation indicated Fermi level pinning and substantial band bending in GaN at the interface. Lastly, we illustrate how the depletion regions are formed in a bipolar junction with an ultrathin monolayer component using the calculated distribution of the charge density across the /GaN junction.