Self-catalyzed metal organic chemical vapor deposition growth of vertical β-Ga2O3 nanowire arrays

Abstract

Self-catalyzed metal organic chemical vapor deposition (MOCVD) growth of Ga2O3 nanowires on GaN layers prepared on a sapphire substrate has been studied. Nanowire orientations are found to be growth temperature dominated. The vertical yields over total (VOT) curve shows a maximum peak beyond 70% around 480 °C, based on scanning electron microscope observations. X-ray diffraction patterns revealed a primary β-(-201) normal orientation of as grown nanowires all over the studied temperature interval. Further transmission electron microscopy characterization had confirmed β-(-201) normal axial orientation of these vertical nanowires, which have well crystallinity. The β-(010)//GaN(110) in-plane epitaxial relationship is consistent with reported Ga2O3 film/nanowire growth. Nanowires crystallized in β-[001] axial orientation were considered to be the inclined ones. Based on contrast experiments, the temperature dominated growth behavior is considered a thermodynamic process. The two observed crystalline orientation might have distinguishable but similar system energy, which results in coexistence of multi orientation nanowires over a large temperature span and an optimum temperature window for vertical β-(-201) normal orientation. The presented optimized β-Ga2O3 nanowire arrays with highest VOT close to 90% should effectively promote development of reliable high performance devices based on Ga2O3 nanowires.