Dislocation dynamics in α-Ga2O3 micropillars from selective-area epitaxy to epitaxial lateral overgrowth

Abstract

Epitaxial lateral overgrowth (ELO) is an effective strategy to achieve metastable phased α-Ga2O3 with low dislocation densities, which is desirable for developing ultralow-loss and ultrahigh power devices, whereas the involved dislocation dynamics have not been fully exploited. In this Letter, we investigated the dislocation propagations and reactions in α-Ga2O3 micropillar arrays selectively grown by halide vapor phase epitaxy technique. Screw dislocations in α-Ga2O3 micropillars grown from the selective area epitaxy (SAE) to ELO mode exhibited an independent character with an average density of 4.5 × 106 cm−2 while the edge dislocation density was reduced to 5.3 × 108 cm−2. During the initial SAE process, the α-Ga2O3 hexagonal pyramid is developed with the observed inversion domains within the pillar cores. The successive epitaxial lateral overgrowth ELO facilitates the formation of inclined facets upon the SiO2 mask. Almost complete filtering of the underlying threading dislocation has been demonstrated in the ELO wings. Strong image forces induced by inclined free surfaces drive the propagation and reaction of threading dislocations until annihilation, which is well described by the dislocation-filtering model during the dynamic geometry transition of micropillars. These findings may pave the way for the success of the heteroepitaxy of low dislocation density α-Ga2O3 toward the development of high-performance power devices.