Unveiling Superior\nSolar-Blind Photodetection with\na NiO/ZnGa<sub>2</sub>O<sub>4</sub> Heterojunction Diode

This investigation presents a self-powered, solar-blind\nphotodetector\nutilizing a low-temperature fabricated crystalline NiO/ZnGa<sub>2</sub>O<sub>4</sub> heterojunction with a staggered type-II band alignment.\nThe device leverages the pyrophototronic effect (PPE), combining the\nphotoelectric effect in the p–n junction and the pyroelectric\neffect in the non-centrosymmetric ZnGa<sub>2</sub>O<sub>4</sub> crystal.\nThis synergistic effect enhances the photodetector’s performance\nparameters, thereby outperforming traditional solar-blind photodetectors.\nThe device demonstrates an extremely low dark current of 5.39 fA,\na high responsivity of 88 mA/W, and a very high specific detectivity\nof 2.03 × 10<sup>14</sup> Jones under 246 nm light irradiation\nat 0 V bias. Significantly, due to the PPE, the impact demonstrates\na much-enhanced transient response when tested under various light\nintensities, ranging from 18 to 122 μW/cm<sup>2</sup>. The photodetector\nshows a high responsivity of 338 A/W and an outstanding detectivity\nof 7.1 × 10<sup>18</sup> Jones with an applied voltage of −13\nV, showing its ability to detect weak signals. Single-crystalline\nZnGa<sub>2</sub>O<sub>4</sub> fabricated by MOCVD exhibits significant\nabsorption of deep UV light, and the heterojunction’s type-II\nband alignment with NiO is responsible for its exceptional self-powered\npyrophotoelectric detecting and rectifying capabilities.