Surface pretreatment and deposition temperature dependence of MgO epitaxy on GaN by thermal atomic layer deposition

•Thermal atomic layer deposition of magnesium oxide on gallium nitride templates was performed and studied.•ALD deposition temperatures >250° C are preferable for high quality MgO eplayers.•The MgO forms with [1 1 1] parallel to the surface but in two distinct domains rotated in-plane by 60°. We report on the structural properties of MgO films deposited on GaN templates on sapphire substrates via atomic layer deposition (ALD). Analysis of the crystal quality and structure as a function of surface treatment and growth temperature are presented. Our results indicate deposition temperatures greater than 250 °C are preferable for achieving a high quality MgO thin film. Rotational scans of the samples show a six-fold symmetry at all deposition temperatures, indicating the existence of two rotational symmetric MgO crystal domains on the GaN surface, which were confirmed using electron backscatter diffraction.