Editors’ Choice—Structural, Electrical, and Luminescent Properties of Orthorhombic κ-Ga₂O₃ Grown by Epitaxial Lateral Overgrowth

Abstract

The properties of orthorhombic κ-Ga2O3 films grown by Epitaxial Lateral Overgrowth (ELOG) were studied by Scanning Transmission Electron Microscopy (STEM), X-ray diffraction, capacitance-voltage profiling, Microcathodoluminescence (MCL) spectroscopy and imaging. ELOG mask was formed by deposition of SiO2 stripes on TiO2 buffer prepared on basal plane sapphire, with the stripes going along the [11 2 ̅ 0] direction of sapphire. κ-Ga2O3 ELOG growth was performed using Halide Vapor Phase Epitaxy (HVPE), with ELOG wing of the structure formed by lateral overgrowth over the 20 μm-wide SiO2 stripes, while growth in between the stripes proceeded initially by vertical growth in the 5-μm-wide windows. TEM analysis showed that the material in the windows comprised 120o rotational nanodomains typical of κ-Ga2O3, while, in the wing regions, the material was single-domain monocrystalline. The films were conducting, with the net donor density close to 1013 cm−3. The data suggested the material in the windows have much higher resistance than in the wings. MCL spectra and imaging revealed much higher density of nonradiative recombination centers in the windows than in the wings.

Optical properties of Ga2O3 thin films grown by atomic layer deposition using GaI3 and O3 as precursors

“…In previous studies, the kand e-Ga 2 O 3 have mainly been observed in the films epitaxially grown on a-Al 2 O 3 (0 0 1) (c-cut sapphire) substrates, 7,9,20,25,31,41,[45][46][47][48] whereas only in a few cases have the substrate temperatures below 500 1C been sufficient for formation of these phases. 25,48 Moreover, a relatively complex method, that is, epitaxial lateral overgrowth, including the deposition of the TiO 2 seed layer on c-sapphire and a following lithography process to form a pattern that supports the k-Ga 2 O 3 growth, has been developed 53 and applied 54 for improving the quality of k/e-Ga 2 O 3 films. However, even in these cases, substrate temperatures of 540-570 1C have been used for deposition of the films by halide vapour phase epitaxy.…”

“…However, even in these cases, substrate temperatures of 540-570 1C have been used for deposition of the films by halide vapour phase epitaxy. 53,54 Hence, the thermal ALD based on GaI 3 and O 3 provides a much simpler approach for deposition of films containing k-Ga 2 O 3 .…”