Heteroepitaxial β-Ga 2 O 3 on Conductive Ceramic Templates: Toward Ultrahigh Gain Deep-Ultraviolet Photodetection

This article investigates the ultrahigh sensitivity and DUV photodetection capability of a hybrid oxide-nitride stack comprising β-Ga2O3 layers grown heterogeneously on a conductive ceramic crystal. The ceramic crystal, namely a TiN interlayer, which acts as a lattice template, was heteroepitaxially grown on bulk MgO. Because β-Ga2O3 is a monoclinic phase crystal, it is conjectured that its nucleation and growth process on cubic phase TiN is entropic in nature, whereby the two unit cell configurations of the β-Ga2O3 crystal, exhibiting rotational twin domains, grew alternately side by side in a semiperiodic manner on TiN while maintaining a single crystal phase. This film formation mechanism contributed to the introduction of additional defects in the β-Ga2O3 lattice (Taylor's dislocations in addition to growth-induced vacancies). The fabricated DUV photodetectors based on the resulting metal-semiconductor junction heterodiodes exhibited an average peak spectral responsivity of 276.72 A W−1 and fast decay constants in the order of 500 ms in the ultraviolet-C regime, with true solar-blind characteristics manifested by ultraviolet-to-visible rejection ratios of up to 2 × 103 and illuminating power density of around 70 μW cm−2. The crystallographic orientation relationships between the TiN and β-Ga2O3 crystals, as well as the lattice fit and dislocation types, are revealed and examined.