Boosting interface band alignment via synergistic supercritical fluid post-treatment and SAM functionalization for Ga2O3-hybrid solar-blind detectors

Abstract

p-n heterojunction solar-blind photodetectors, based on p-type materials and n-type Ga₂O₃, have attracted significant attention in the optoelectronics field due to their inherent low dark current and self-powered operation. Among various constructions, organic-inorganic hybrid heterojunctions formed by integrating p-type organic materials with n-type Ga₂O₃ offer a promising solution to overcome the lattice mismatch, opening new avenues for device performance breakthroughs. In this work, the Ga₂O₃ thin films are treated via a supercritical fluid technique (SC), which significantly reduced defect state density while improving crystallinity and surface uniformity of films, thereby laying a crucial foundation for heterojunction interface optimization. Simultaneously, a self-assembled monolayer (SAM) was introduced at the organic-inorganic heterojunction interface. Notably, the high-quality Ga₂O₃ surface engineered via the supercritical fluid treatment facilitated the highly efficient, oriented self-assembly of SAM molecules, enabling precise modulation of the interfacial energy band alignment and promoting the separation and transport dynamics of photogenerated carriers. Benefiting from the synergistic effects of supercritical fluid modification and SAM functionalization, the fabricated solar-blind photodetector achieves a highest responsivity of 111.7 mA/W and a specific detectivity of 1.02 × 10¹¹ Jones under zero bias (self-powered mode) and weak 254 nm light with an intensity of 5 µW/cm².