Monolithic Epitaxial Integration of β-Ga<sub>2</sub>O<sub>3</sub> with 100 Si for Deep Ultraviolet Photodetectors
Sandeep Vura, Usman Ul Muazzam, Vishnu Kumar, Sai Charan Vanjari, R. Muralidharan, Nath Digbijoy, Pavan Nukala, Srinivasan Raghavan
Abstract
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.