Transistor-esque operation permits high performance of UV photodetector

Lyu et al. built a high performing ultraviolet (UV) photodetector that could lead to applications in aerospace engineering, flame detection, ozone sensing and advanced communications.

The authors’ photodetector simultaneously demonstrated a high UV-to-visible rejection ratio, high photo-to-dark current ratio, and high responsivity. These properties allow the device to be very sensitive to UV light detection but ignore background light noise of wavelengths within the visible spectrum range or longer.

p-GaN/AlGaN/GaN heterostructures were pivotal to the photodetector’s success. These heterostructures, which were grown on cost-effective silicon substrates, are often used in GaN high-electron-mobility transistors.

The authors determined their photodetector containing p-GaN/AlGaN/GaN heterostructures operated like a transistor, exhibiting high electrical gain compared to traditional photodetectors. The device’s high electrical gain allowed a high photocurrent under UV illumination, and the effective p-GaN optical gate depletion led to a low standby current in a dark environment, which together result in the high photo-to-dark current ratio. They believe this device’s operational mechanism is applicable to other photodetectors with similar structures.

“Our work can facilitate the UV photodetector design and further advance the device performance,” said author Kei May Lau. “The demonstration of our photodetectors on low-cost silicon substrates paves the way for their wide adoption in applications.”

The researchers will attempt to quicken the response time of the photodetector without decreasing its responsivity. They also want to explore combining photodetectors with other electronic devices, such as LEDs, diodes, and transistors.

Source: “High gain and high ultraviolet/visible rejection ratio photodetectors using p-GaN/AlGaN/GaN heterostructures grown on Si,” by Qifeng Lyu, Huaxing Jiang, and Kei May Lau, Applied Physics Letters (2020). The article can be accessed at https://doi.org/10.1063/5.0011685 .