Preparation of a Ta2O5–SiO2 composite bilayer using electron beam evaporation for the surface passivation of In0.83Ga0.17As PIN photodetectors

High-indium-content In0.83Ga0.17As is the key material for extended short-wave infrared (eSWIR) photodetectors operating in the 1.7–2.7 μm range. Here, we demonstrate a Ta2O5–SiO2 bilayer passivation structure, deposited by electron beam evaporation, on In0.83Ga0.17As PIN mesa photodetectors. The bilayer delivers stable dark current suppression across a wide bias range, maintaining a surface leakage current density of 2.2 × 10−6 A/cm2 at high bias and achieving a room-temperature sidewall resistivity up to 106 Ω cm. X-ray photoelectron spectroscopy reveals that lattice oxygen in Ta2O5 forms stable As–O bonds with surface arsenic atoms, effectively breaking Fermi-level pinning, while the outer SiO2 layer ensures long-term environmental stability. This work provides an efficient and scalable passivation route for high-In mesa-type eSWIR detectors. The device achieves a specific detectivity of 9 × 1011 Jones at 200 K.