Interface Formed via Spontaneous Phase Transition from α- to κ-Ga2O3

초록

In this work, we investigated the heterointerface formed between metastable alpha-Ga2O3 (corundum) and kappa-Ga2O3 (orthorhombic). When kappa-Ga2O3 was grow on c-plane sapphire at temperatures above 570 degrees C via mist chemical vapor deposition, alpha-Ga2O3 initially formed, followed by a spontaneous phase transition from alpha- to kappa-Ga2O3, resulting in an atomically abrupt interface. Despite this abrupt interface, the process was uncontrolled, leading to an uneven interface on a micrometer scale. To address this, the growth process was optimized, identifying strain and temperature as the key control parameters to achieve a uniform and atomically abrupt interface. The band offset at the kappa-/alpha-Ga2O3 interface was analyzed using X-ray photoelectron spectroscopy. The results revealed a type-II band alignment, with the valence and conduction bands of kappa-Ga2O3 positioned approximately 1.00 and 0.80 eV higher, respectively, than those of alpha-Ga2O3. This was further corroborated by density functional theory calculations. The observed band offset at the pristine kappa-/alpha-Ga2O3 interface holds promise for advanced device designs, offering potential applications in future electronic and optoelectronic technologies.

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