ScAlMgO4 (SAM) has attracted attention as a substrate for nitride semiconductor crystal growth owing to its small a-axis lattice mismatch with GaN and InGaN. In this study, we investigated GaN growth on an SAM substrate via radio-frequency plasma-excited molecular beam epitaxy. By optimizing the growth conditions, GaN with the following epitaxial orientation relations (0001)GaN//(0001)SAM and [11-20]GaN//[11-20]SAM was successfully grown directly on the SAM substrate. The atomically flat and abrupt interface of GaN directly grown on the SAM substrate was observed via high resolution transmission electron microscopy, and uniform GaN growth on a two-inch SAM substrate was also demonstrated.

ScAlMgO4 (SAM) substrates have a trigonal structure with high cleavability in the c-plane. Because this substrate can be easily cleaved, gallium oxide (Ga2O3) can be grown on the SAM substrate, and it may be possible to solve the problem of the difficulty in the heat dissipation of Ga2O3. Therefore, in this study, we performed Ga2O3 growth on a SAM substrate using mist chemical vapor deposition. When the growth temperature was varied at 500, 600, and 700 °C, ε-Ga2O3(004) grew dominantly, and the crystallinity improved with increasing temperature. It was also suggested that the grown ε-Ga2O3 formed rotational domains of 120°. Furthermore, a phase transition to β-Ga2O3 was achieved by annealing the resulting ε-Ga2O3 on the SAM substrates. We also succeeded in separating the SAM substrates on which the Ga2O3 thin films were grown.