关键词: growth mode, miscut angle, crystalline quality, surface morphology

Abstract: Controlling the epitaxial growth mode of semiconductor layers is crucial for optimizing material properties and device performance. In this work, the growth mode of $\alpha $-Ga$_{2}$O$_{3}$ heteroepitaxial layers was modulated by tuning miscut angles ($\mathrm{\theta })$ from 0$^\circ$ to 7$^\circ$ off the (10$\bar 1$0) direction of sapphire (0002) substrate. On flat sapphire surfaces, the growth undergoes a typical three-dimensional (3D) growth mode due to the random nucleation on wide substrate terraces, as evidenced by the hillock morphology and high dislocation densities. As the miscut angle increases to $\theta =5^\circ$, the terrace width of sapphire substrate is comparable to the distance between neighboring nuclei, and consequently, the nucleation is guided by terrace edges, which energetically facilitates the growth mode transition into the desirable two-dimensional (2D) coherent growth. Consequently, the mean surface roughness decreases to only 0.62 nm, accompanied by a significant reduction in screw and edge dislocations to 0.16$\times 10^{7}$ cm$^{-2}$ and 3.58$\times10^{9}$ cm$^{-2}$, respectively. However, the further increment of miscut angles to $\theta =7^\circ$ shrink the terrace width less than nucleation distance, and the step-bunching growth mode is dominant. In this circumstance, the misfit strain is released in the initial growth stage, resulting in surface morphology degradation and increased dislocation densities.

Key words: growth mode, miscut angle, crystalline quality, surface morphology