Abstract
We demonstrate the epitaxial lateral overgrowth of α-Ga2O3 by halide vapor phase epitaxy. We prepared patterned SiO2 masks on a (0001) α-Ga2O3/sapphire template, and then α-Ga2O3 islands were regrown selectively on the mask windows. The islands grew vertically and laterally to coalesce with each other. Facet control of the α-Ga2O3 islands was achieved by controlling the growth temperature, and inclined facets developed by decreasing the temperature. Transmission electron microscopy revealed that the crystal quality of the regrown α-Ga2O3 was improved owing to both the blocking of dislocations by the mask and the dislocation bending by the inclined facets.
Highlights
To improve the crystal quality of heteroepitaxial films grown on highly mismatched substrates, such as GaN on sapphire, the epitaxial lateral overgrowth (ELO) technique has been shown to be effective.7–9 In this technique, epitaxial growth is performed on a seed layer (GaN on sapphire, for example) with a periodically patterned mask on the surface
Dislocations in the seed layer propagate into the grown layer through the windows, the dislocations bend toward the lateral direction to minimize the elastic strain energy if the islands have inclined facets
halide vapor phase epitaxy (HVPE) is a type of CVD technique that is characterized by a fast growth rate, and the HVPE of α-Ga2O3 has already been demonstrated
Summary
To improve the crystal quality of heteroepitaxial films grown on highly mismatched substrates, such as GaN on sapphire, the epitaxial lateral overgrowth (ELO) technique has been shown to be effective.7–9 In this technique, epitaxial growth is performed on a seed layer (GaN on sapphire, for example) with a periodically patterned mask on the surface. The ELO technique is essential to grow high-quality GaN by heteroepitaxy, and the threading dislocation density reduces typically from 109 cm−2 to 106 cm−2 or less.7–9 The ELO of α-Ga2O3 has already been demonstrated.10 In the demonstration, a stripe-patterned SiO2 mask with a mask/window size of 2 μm/2 μm was formed directly on a (0001) sapphire substrate, and α-Ga2O3 was grown by mistCVD.
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