Unlocking the Single-Domain Heteroepitaxy of Orthorhombic κ-Ga 2 O 3 via Phase Engineering

作者：Yijun Zhang, Yiqing Gong, Xuanhu Chen, Yue Kuang, Jinggang Hao, Fangfang Ren, Shulin Gu, Rong Zhang, Jiandong Ye · 发表于：ACS Applied Electronic Materials · 年份：2021 · DOI：10.1021/acsaelm.1c01094 · 被引用次数：32 · 研究领域：Ga2O3 and related materials、Perovskite Materials and Applications、Multiferroics and related materials

The emergent ferroelectric property of κ-Ga 2 O 3 is expected to deliver advanced functional memory and ultralow-loss transistors, while the commonly observed rotational domains in κ-Ga 2 O 3 make the origin of ferroelectricity mysterious. In this work, the single-domain heteroepitaxy of orthorhombic κ-Ga 2 O 3 epilayers on sapphire has been demonstrated by the halide vapor-phase epitaxy (HVPE) technique. The optimal temperature of 550 °C is energetically favorable for the stabilization of κ-Ga 2 O 3 on sapphire without impurity phases, and the growth dynamics is dominated by the surface-reaction-limited mechanism. The evolution of microstructures and optical characteristics indicate that the κ–β phase transition occurs at an elevated temperature of over 575 °C together with a remarkable reduction of growth rate. With proper phase engineering, the single-domain κ- Ga 2 O 3 epilayers have been ultimately achieved, exhibiting multisteps resembling a terrace morphology, a relatively low screw dislocation density of 5.2 × 10 7 cm –2, and reduced band tail subgap states. The single-domain structure of orthorhombic κ-Ga 2 O 3 was identified by the XRD ϕ-scans and transmission electron microscopic analysis. The realization of single-domain epitaxy allows one to uncover the driving force for the intriguing ferroelectric behavior of κ-Ga 2 O 3 and to design power devices with improved performance.