Polymorphism and Faceting in Ga<sub>2</sub>O<sub>3</sub> Layers Grown by HVPE at Various Gallium‐to‐Oxygen Ratios
Sevastian Shapenkov, О. Ф. Вывенко, В. И. Николаев, С. И. Степанов, А. И. Печников, M. P. Scheglov, Georgiy Varygin
Abstract
Herein, the influence of the oxygen flow on the formation of metastable polymorphs of gallium oxide (Ga 2 O 3 ) grown by halide vapor phase epitaxy (HVPE) on c‐plane patterned sapphire substrates (PSS), on gallium nitride (GaN) templates, and on m‐plane smooth sapphire substrates is reported. X‐ray diffraction, scanning electron microscopy, and cathodoluminescence are used to identify different polymorphic phases. The samples deposited on bare PSS exhibit faceted growth of the α‐Ga 2 O 3 on the cones of the sapphire substrate and the formation of the κ‐Ga 2 O 3 between the cones. In contrast, growth on GaN templates results in hexagonal columns of κ‐Ga 2 O 3 which produce a continuous smooth layer upon coalescence. The growth of Ga 2 O 3 on m‐plane sapphire substrates results in overgrown pyramids of the α‐phase. For all types of substrates, the variation of the oxygen flow affects only the thickness and coalescence of Ga 2 O 3 layers. Thus, the growth of Ga 2 O 3 metastable polymorphs is mainly influenced by the form, orientation, and symmetry of the substrate and shows a weak dependence on stoichiometry.