Contact engineering speeds up solar-blind photodetectors

As an ultra-wide bandgap semiconductor, gallium oxide is a promising material for solar-blind ultraviolet photodetectors, which detect short-wavelength ultraviolet light while

ignoring infrared, visible, and longer-wavelength ultraviolet light. These photodetectors have potential applications in optical communications, biomedical imaging, environmental monitoring, astrophysics, and security.

However, the slow response time of gallium oxide photodetectors — hundreds of milliseconds — has hindered their commercial application. To remedy this, Sang et al. designed and constructed solar-blind ultraviolet photodetectors using gallium oxide as the semiconductor and palladium as the contact electrode.

Previous gallium oxide-based photodetectors often employed titanium as the contact electrode. But palladium has a higher work function, which means it takes more energy to remove electrons. This allows for more precise control of electron emission across its interface with gallium oxide.

“By using single-crystal palladium electrodes, the performance of gallium oxide ultraviolet photodetectors has been greatly improved,” said author Wei Han.

The photodetectors demonstrated a faster photoelectric response time, 2.4 milliseconds, and a larger linear dynamics range, meaning they accurately detect light over a wider range of intensities.

In addition to materials selection, the quality of the interface between the semiconductor and the electrodes can affect photodetector performance. Defects, impurities, and disorder at the interface will slow down the device. The authors used high-vacuum electron-beam evaporation to deposit the palladium electrodes on the surface of the gallium oxide. Transmission electron microscopy showed the contact interface was clean and smooth.

The performance of these solar-blind ultraviolet photodetectors suggests they could be used in ultraviolet communication and imaging applications.

“Our next step will be to optimize the performance and conduct research on productization,” said author Hao Wang.

Source: “Enhanced linear dynamic range and response speed in interdigital-electrode solar-blind photodetector by contact engineering,” by Kangren Sang, Jiayun Wei, Wei Han, Ziyu Chu, Hui Yuan, Chenguang Guo, Jinlong Liu, Qihang Sun, Longhui Zeng, Liangping Shen, Jun Yuan, Qiangmin Wei, and Hao Wang, Applied Physics Reviews (2025). The article can be accessed at https://doi.org/10.1063/5.0269272 .