Toward superior MgZnO tunnel and Schottky devices: The role of hydrogen impurity removal

Abstract

Controlling hydrogen incorporation in wide-bandgap semiconductors is increasingly recognized as a key requirement for achieving reliable performance in next-generation electronic, optoelectronic, and spintronic devices. In wurtzite MgZnO, hydrogen acts simultaneously as an unintentional shallow donor and an interface-active species, strongly modifying band alignment, barrier formation, and Mg incorporation efficiency. In this work, we report the epitaxial growth of (0001)-oriented single-phase wurtzite Mg x Zn 1 − x O thin films on Pt/Co 0.30 Pt 0.70 (111) electrodes using oxygen plasma-assisted molecular beam epitaxy. We systematically quantify the impact of hydrogen residues on the electronic properties of the resulting metal/oxide interfaces. Analysis of MgZnO-based tunnel junctions using the Brinkman–Dynes–Rowell model, together with back-to-back Schottky diode characteristics, reveals that residual hydrogen significantly reduces both the tunneling barrier and the Schottky barrier heights by ∼ 40 meV and ∼ 240 meV, respectively, for an existing effective hydrogen concentration on the order of 1 0 19 cm − 3 . Removing hydrogen suppresses the unintentional n -type conductivity, enhances Mg incorporation in the initial growth layers, and restores a higher interfacial potential barrier. These findings demonstrate that the Pt/CoPt/MgZnO hetero-structure is highly sensitive to hydrogen-related defects, and that precise hydrogen control is essential for engineering predictable band alignment and transport characteristics. The resulting tunability positions MgZnO on ferromagnetic CoPt as a promising platform for emerging opto-spintronics applications, including electrically driven spin-LEDs and spin-controlled ultraviolet photonic devices. • Hydrogen removal increases SBH at CoPt/MgZnO and Pt/MgZnO by up to 237 meV. • Thermionic leakage at –2 V is suppressed by five orders of magnitude after H 2 removal. • Tunneling barrier height and width increase by ∼ 40 meV and ∼ 1.5 nm, respectively. • Hydrogen dipole model links 240 meV SBH shift to ∼ 1.7 × 1 0 19 cm − 3 H concentration. • Epitaxial MgZnO forms a bilayer structure with tunable Mg content and no ZnO-like interlayer.