Ge-doping-induced phase engineering of β/ε-Ga2O3 for high-performance ultraviolet detectors

Abstract

Solar-blind deep-ultraviolet (DUV) photodetectors based on intrinsic Ga₂O₃ typically suffer from a trade-off between low responsivity and high dark current due to poor carrier transport and high defect densities. To overcome these bottlenecks, this work utilizes mist chemical vapor deposition (Mist-CVD) to fabricate Ge-doped Ga₂O₃ films, successfully constructing a high-quality β/ε heterophase homojunction. Ge incorporation effectively relaxes lattice strain, suppresses cation vacancies, and restores the Ga/O stoichiometry to a near-ideal ratio. Crucially, the induced β/ε interface naturally forms a Type-II staggered band alignment with a strong built-in electric field. This architecture suppresses dark current via a high potential barrier while enabling a giant photoconductive gain through a hole-trapping-induced photogating effect under illumination. Consequently, the Ge-doped MSM photodetector exhibits superior performance, maintaining a low dark current of 10⁻¹⁰ A (@ 50 V). Notably, it achieves a peak responsivity of 160 A W⁻¹ (@ 40 V), a specific detectivity of 4.81 × 10¹⁴ Jones, and a PDCR of 2.3 × 10⁵, representing a significant four-order-of-magnitude enhancement compared to the undoped counterpart. These results validate Ge-induced phase engineering as a promising strategy for developing high-sensitivity, low-noise DUV sensing applications.