Structural characterization and optimization of PAMBE-grown Ga2O3 on STO (001)*

Wide band-gap semiconductor Ga2O3 is in the focus of research as a promising material for high-power device applications. Here, we report on the structural properties of Ga2O3 grown by plasma-assisted MBE on STO as a function of growth temperature. At elevated temperatures above 550 °C we observe two out-of-plane orientations of the beta-polymorph (1-2-2) and (100), each with four in-plane rotational domain orientations by XRD and RHEED. As we lower the temperature the high-energy surface (1-2-2) becomes suppressed and we obtain single-out-of-plane oriented (100) beta-Ga2O3. The possibility of thin interfacial layers of gamma-Ga2O3 is investigated by means of STEM. The relevance of the integration of Ga2O3 on STO is that STO can be epitaxially grown directly on Si (001) and hence, can function as a template layer for the integration of Ga2O3 onto the Si platform. A low temperature growth is therefore preferable.