Monolithic Epitaxial Integration of β-Ga₂O₃ with 100 Si for Deep Ultraviolet Photodetectors

In this report, we demonstrate direct epitaxial integration of β-Ga2O3 on a (400) oriented silicon on insulator substrate toward deep-UV (DUV) optoelectronics. The 550 nm thick (400) epitaxial-β-Ga2O3 films are deposited onto Si(100) using a two-step buffer and a two-step epilayer scheme. The epitaxial orientation relation between β-Ga2O3, MgO, and silicon(100) is given by (400)β-Ga2O3||(100)MgO||(100)Si and ⟨010⟩β-Ga2O3||⟨011⟩MgO||⟨110⟩Si. The presence of rotational variants is confirmed by X-ray diffraction and transmission electron microscopy. Epitaxy was found to be mediated through a MgGa2O4 layer formed at the β-Ga2O3/MgO interface under oxygen-deficient conditions during pulsed layer deposition. The ω-scan symmetric and asymmetric full width at half-maximum values of β-Ga2O3 are 2.41 and 2.39°, respectively. Photodetectors realized in a conventional metal–semiconductor–metal geometry exhibit a maximum responsivity of 11.8 A/W at 246 nm at 40 V with a photo to dark current ratio of 2.5 × 102 and a UV-to-visible rejection ratio > 103. The detectors do not exhibit any persistent photoconductivity as is evident from the rise and fall times of 0.54 and 0.32 s, respectively. Such a monolithic integration of β-Ga2O3 on Si(100) opens up opportunities for the development of integrated DUV focal plane arrays on a SoC chip.