N-Barrier-N Ga2O3 Photodetector Achieving Ultralow Equivalent Noise Power for Solar-Blind Detection

Abstract

Solar-blind photodetectors operating in the deep ultraviolet (DUV) spectrum are critical for applications. However, the severe attenuation of DUV signals in the atmosphere demands photodetectors with ultralow noise and high sensitivity to resolve weak optical signals. Here, we report a breakthrough in β-Ga₂O₃-based n-Barrier-n (nBn) unipolar heterostructure photodetectors that synergistically address these challenges. By employing a β-Ga₂O₃/LaAlO₃/Nb:SrTiO₃ heterojunction fabricated via laser molecular beam epitaxy, we engineer a large conduction band offset and near-zero valence band offset, creating a unipolar electron transport channel that suppresses dark current to subpicoampere levels (<1 pA). The device exhibits exceptional performance metrics: a responsivity of 853.6 A/W, an external quantum efficiency of 4.2 × 10⁵%, and a record-low noise-equivalent power (NEP) of 0.7 ± 0.1 fW/Hz^1/2─surpassing state-of-the-art DUV detectors. These advancements are attributed to the high dielectric constant (∼24) and lattice compatibility of LaAlO₃ with Nb:SrTiO₃, which minimize interfacial defects and enhance carrier confinement. This work not only establishes a new paradigm for Ga₂O₃-based optoelectronics but also provides a universal design strategy for high-sensitivity, low-noise photodetectors in photon-starved environments, with transformative potential for deep-space communication and ultraviolet astronomy.