Solar-blind ultraviolet photodetectors enhanced with hafnium oxide

In complexly lit environments, getting high signal-to-noise ratios with photodetectors can be challenging. However, clear signals can be reliably obtained in a spectral region from 200 to 280 nanometers, where the atmosphere blocks nearly all sunlight. One promising technology that can leverage this spectral region is solar-blind ultraviolet photodetectors. Yet these detectors face limitations such as the scarcity of suitable material systems, poor compatibility with CMOS processes, and the difficulty in precisely matching the bandgap of existing materials to the solar-blind ultraviolet spectrum, which determines the energy threshold for a photon to be absorbed.

To improve solar-blind ultraviolet photodetectors, Wu et al. designed a silicon-based detector with hafnium oxide (HfO₂), which has a large bandgap and low intrinsic carrier concentration. Using band engineering, the researchers were able to modify the band structure and conductive properties of the hafnium oxide. They additionally used graphene to enhance separation and transport efficiency. The resulting photodetector showed excellent spectral selectivity with a high solar-blind-visible rejection ratio of 2039.

“The most exciting aspect is that we pioneeringly applied HfO₂ — a material commonly used in chip manufacturing — to the field of solar-blind ultraviolet detection by combining band engineering with graphene,” said author Qichang Hu. “This achievement enables silicon-based integration compatible with CMOS processes, opening new pathways for the large-scale integration and commercialization of solar-blind ultraviolet detectors.”

The researchers hope their findings can be applied to optoelectronic chips to advance large-scale integration of solar-blind ultraviolet photodetectors. These detectors could ultimately be used in a wide range of cases from corona discharge monitoring to fire detection to secure communications. Next, the researchers plan to improve the performance parameters of solar-blind ultraviolet photodetectors and explore more applications for them.

Source: “Synergistic dual built-in electric fields and HfO₂ band engineering for self-powered solar-blind UV detectors on silicon,” by Ziming Wu, Linfeng Ye, Zihan Lin, Linlei Jiang, Shuai Li, Banghao Xie, Yufei Liu, and Qichang Hu, Applied Physics Letters (2025). The article can be accessed at https://doi.org/10.1063/5.0290624 .