Anisotropic photoresponse behavior of a LaAlO₃ single-crystal-based vacuum-ultraviolet photodetector

Nowadays, vacuum-ultraviolet (VUV) photodetectors (PDs) have attracted extensive attention owing to their potential applications in space exploration, radiation monitoring, and the semiconductor industry. Benefiting from its intrinsic ultra-wide band-gap, chemical robustness, and low-cost features, LaAlO₃ shows great promise in developing next-generation compact, cheap, and easy-to-fabricate VUV PDs. In this work, we report the unique anisotropic photoresponse behavior of LaAlO₃ single crystals for VUV photodetection applications. First of all, with the guidance of density functional theory (DFT) calculations along with the comprehensive material characterization, the anisotropic carrier transport behavior of LaAlO₃ single crystals was confirmed. Thereafter, after exploring the metal-semiconductor-metal (MSM) device configuration along different substrate orientations, including (100), (110), and (111)-LaAlO₃ single crystals, we found that the (110)-LaAlO₃ VUV PD exhibits the best device performance under VUV illumination, with a responsivity of 2.23 mA W^-1, a high detectivity of 3.72 × 10¹¹ Jones, and a photo-to-dark-current ratio of 5.48 × 10³. This work not only provides a feasible avenue to explore the anisotropic optoelectronic behavior of ultra-wide band-gap semiconductors but also expands the application of the low-cost oxide perovskite family in the field of VUV photodetection.