Beta to Spinel Phase\nTransition of Magnesium Gallium\nOxide Thin Films and Their Photoluminescence Properties

As a promising Ga<sub>2</sub>O<sub>3</sub>-based ultrawide\nbandgap\nsemiconductor, beta (β) phase and spinel phase magnesium gallium\noxide (MgGaO) with tunable bandgap larger than 4.8 eV has great potential\nin power electronics and deep ultraviolet optoelectronics. However,\nthe role of Mg composition on the phase transition of MgGaO thin films\nfrom the β to spinel phase and their photoluminescence (PL)\nproperties are still not explored. In this perspective, nine MgGaO\nsamples with Mg atomic percent from 0 to 15.26% were grown by using\noxygen plasma assisted molecular beam epitaxy. Bandgap tuning from\n4.86 to 5.45 eV in MgGaO alloys was observed. The phase transition\nbetween β-MgGaO and spinel MgGa<sub>2</sub>O<sub>4</sub> thin\nfilms was confirmed, and lattice parameters changing with Mg at. %\nwere extracted by X-ray diffraction theta/2theta scans and in-plane\nreciprocal space mapping. Room temperature-, power-, and temperature-dependent\nPL properties of these MgGaO films were investigated, and the PL mechanisms\nwere revealed.