Epitaxial growth of a beta-Ga2O3 (-201)-oriented thin film on a threefold symmetrical SrTiO3 (111) substrate for heterogeneous integration

Epitaxial growth of a wide bandgap semiconductor beta-Ga2O3 thin film with high crystal quality plays a decisive role in constructing optical and electronic devices. However, except for the native substrate, the scarcity of appropriate non-native substrates or the poor crystallization of the deposit in thin film growth severely limits the fabrication and applicability of the final heterostructures and devices. Here, by taking the consistent symmetry and closely matched atomic spacing between beta-Ga2O3 (-201) and the cubic perovskite (111)-oriented plane of SrTiO3, we realize the epitaxial growth of single crystal beta-Ga2O3 (-201) thin films on the SrTiO3 (111) substrate by the pulsed laser deposition method, as confirmed by wide-range reciprocal-space mapping and high-resolution scanning transmission electron microscopy. The fabricated beta-Ga2O3 (-201) photodetector device on the SrTiO3 (111) substrate exhibits excellent ultraviolet optical detection performance with large on/off switching ratios and a fast response speed. Moreover, the beta-Ga2O3/SrTiO3 (111) heterojunction shows type-II heterostructure characteristics for energy band alignment, which displays superior ability for electron-hole pairs separation with large conduction and small valance band offsets of 1.68 and 0.09 eV, respectively. The results offer us a new way to obtain high-quality beta-Ga2O3 (-201) thin film heterostructures on cubic SrTiO3 (111) substrates and fabricate beta-Ga2O3-based optical and electronic devices.