Heteroepitaxial β‐Ga<sub>2</sub>O<sub>3</sub> on Conductive Ceramic Templates: Toward Ultrahigh Gain Deep‐Ultraviolet Photodetection
Nasir Alfaraj, Kuang‐Hui Li, Meshal Alawein, Chun Hong Kang, Laurentiu Braic, C.N. Zoita, A. Kiss, Tien Khee Ng, Boon S. Ooi
Abstract
Abstract This article investigates the ultrahigh sensitivity and DUV photodetection capability of a hybrid oxide‐nitride stack comprising β‐Ga 2 O 3 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‐Ga 2 O 3 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‐Ga 2 O 3 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‐Ga 2 O 3 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 × 10 3 and illuminating power density of around 70 μW cm −2 . The crystallographic orientation relationships between the TiN and β‐Ga 2 O 3 crystals, as well as the lattice fit and dislocation types, are revealed and examined.