UV-Visible Photodetection in Sol-Gel-Derived SnGaO/Si Heterostructures with Annealing Modulation

Photodetectors based on ITO-SnGaO/Si-ITO heterojunctions were fabricated using the sol-gel method and systematically optimized by annealing at temperatures from 300 to 600 °C. The SnGaO thin films exhibited low surface roughness and high optical transparency, with optical band gaps increasing from 3.85 to 4.15 eV due to the Burstein-Moss effect. The incorporation of the SnGaO interlayer significantly enhanced photoelectric performance compared with Si or SnGaO structures. Under 635 nm illumination, as the annealing temperature increased from 300 to 600 °C, the photocurrent (<i>I</i> _light) rose from 1.8 × 10^-4 to 4.6 × 10^-4 A, the light-to-dark current ratio (<i>PDCR</i>) improved from 51.7 to 71.7, responsivity (<i>R</i>) increased from 0.08 to 0.2 A/W, specific detectivity (<i>D</i>*) grew from 2.0 × 10¹⁰ to 3.9 × 10¹⁰ Jones. The device achieved fast response times with less than 1 ms. Under UVB (310 nm) illumination, PDCR increased from 12.0 to 61.9, <i>R</i> from 8.3 × 10^-4 to 3.0 × 10^-2 A/W, and <i>D</i>* from 1.6 × 10⁹ to 2.5 × 10¹⁰ Jones. For UVC (254 nm) light, PDCR reached 38.0, and <i>R</i> increased to 4.8 × 10^-2 A/W after annealing at 600 °C.