On the interpretation of the XRD rocking curves of heteroepitaxial Ga2O3 thin films grown on c-plane sapphire

The present work discusses the two-component structure of out-of-plane x-ray diffraction rocking curves (XRD RCs) of Ga2O3 thin films that are heteroepitaxially grown on c-plane sapphire substrates by ion beam sputter deposition and pulsed laser deposition. The influence of thin film thickness, instrumental resolution, and the deposition method on the RC structure is investigated and the origins of the narrow component are discussed. It is shown that for thin Ga2O3 films on c-plane Al2O3, the narrow component of RCs is not an indication of high crystalline quality, but rather an effect of coherent scattering from a subset of β-Ga2O3 domains with low out-of-plane mosaicity. It was found that the variation of the narrow component intensity with the order of XRD reflection is linked to the presence of antiphase domains (APD), and not to the contribution of the thin interfacial layer of α-Ga2O3.