Achievement of high-performance MISIM-structured Ga2O3-based photodetectors via tailoring of the Al content in AlxHfyO

Abstract

Ga₂O₃ has an ultra-wide bandgap of 4.9 eV, making it an ideal semiconductor material for solar-blind photodetectors (SBPDs). However, a large number of defects are often present in Ga₂O₃ thin films, leading to typically high dark currents in Ga₂O₃-based SBPDs. Although the traditional annealing method is effective in reducing dark current, it often impairs the photoresponse of the fabricated device. In this study, we employ ultra-thin Al_xHf_yO (0 ≤ x, y ≤ 1) insulating layers to modulate the interface electronic structure of the metal–insulator–semiconductor–insulator–metal structured Ga₂O₃-based SBPDs and improve the overall performance of the fabricated SBPDs. For the Ga₂O₃-based SBPD regulated with Al₁Hf₀O (Al₂O₃), the photocurrent increases by approximately 37 times, while the dark current remains nearly unchanged. However, a degradation in both the response time and the cutoff characteristics is observed. In contrast, the SBPD regulated with appropriate stacked Al₂O₃ and HfO₂ materials (Al_0.86Hf_0.14O) exhibits more balanced overall performance, including an ultra-low dark current of 11.28 fA, a specific detectivity of 4.21 × 10¹⁴ Jones, a short decay time of 90 ms, and a responsivity of 2.74 A W⁻¹ at a bias of 20 V. Moreover, a 32 × 32 photodetector array is fabricated using a 1-inch Ga₂O₃ thin film, featuring highly uniform distribution of photocurrent and dark current across the pixels and exceptional imaging capabilities. Based on X-ray photoelectron spectroscopy analysis, a viable physical mechanism based on the interfacial electronic structure and the constructed energy band diagram is proposed to interpret the obtained experimental result for the first time.