Synergistic dual built-in electric fields and HfO2 band engineering for self-powered solar-blind UV detectors on silicon

Abstract

Hafnium oxide (HfO2), renowned for its high dielectric constant and excellent CMOS process compatibility, is a cornerstone material in logic chips. Its wide bandgap and low intrinsic carrier concentration suggest potential for solar-blind ultraviolet photodetection. However, its prohibitively wide bandgap and low conductivity lead to inefficient photogenerated carrier concentration, posing challenges for direct application in solar-blind detection. To overcome these limitations, we incorporate highly conductive In2O3 into HfO2, yielding amorphous InHfO films with a precisely tuned bandgap (Eg ≈ 4.43 eV). Leveraging this material, a self-powered graphene/amorphous InHfO/Si heterojunction solar-blind ultraviolet photodetector is constructed. The synergistic effect of dual built-in electric fields induced by the graphene layer significantly enhances photogenerated carrier separation and collection efficiency, thereby overcoming the inherent limitation of low carrier concentration in the absorber. The device achieves an open-circuit voltage of 0.41 V, with a maximum responsivity of 13.67 mA/W and a detectivity of 2.21 × 1012 Jones at 255 nm under zero bias. The response times are characterized by a rise time of 46 ms and a decay time of 106 ms. Notably, a high solar-blind-visible rejection ratio of 2039 is achieved, underscoring its excellent spectral selectivity. This work pioneers the application of HfO2 in solar-blind ultraviolet photodetection and provides a material system and heterostructure design scheme for silicon-based self-powered solar-blind detectors. Furthermore, it offers an innovative solution for the CMOS-compatible integration of solar-blind UV photodetectors, laying crucial technological foundations for future on-chip optoelectronic sensing units within optoelectronic integrated circuits.