Flame Detection by a β-Ga₂O₃-Based Sensor

An oxide semiconductor of β-Ga2O3 has a natural solar-blind sensitivity due to its large bandgap of 4.8 eV. To evaluate its potential, a flame detector was fabricated using its conductive single crystal substrate applying a simple method without epitaxy and vacuum processes. The structure is a poly(3,4-ethylene dioxythiophene) complex with polystyrene sulfonic acid (PEDOT–PSS) Schottky contact/a semi-insulating layer of β-Ga2O3/n-type region of β-Ga2O3/an In ohmic contact. The spectral response of the detector exhibited a large 250-to-300-nm rejection ratio of 1.5 ×104 and an external quantum efficiency of 18% at 250 nm. The device successfully detected a flame by distinguishing 1.5 nW/cm2 solar-blind light from the flame under a strong fluorescent lamp illumination without any visible-cut filters. This result encourages the fabrication of practical β-Ga2O3-based flame detectors.