New standalone ultraviolet photodetector

April 18, 2023

(Nanowerk News) Ultraviolet (UV) light detection could revolutionize industries such as civil engineering, military defense, aerospace exploration, and medical research. The future of electronics relies heavily on energy efficient devices that can function independently, which makes the development of photoelectric UV detectors important. These detectors come in two main types: photoconductive and photovoltaic, each with unique advantages and applications.

The photoconductive detector relies on the change in the conductivity of the semiconductor under UV light, but requires an external power source, which limits its practical application. Photovoltaic detectors ideally convert optical signals to electrical signals without the need for an external power supply, but they also have low photoresponsiveness, so an external power supply is still required. Also, traditional solid-state UV detectors are complicated to build and not very convenient or cost-effective.

A new photoelectrochemical ultraviolet photodetector (PEC UV PD) device has been developed to detect UV light by using a chemical reaction that generates an electrical signal when exposed to UV light. But most can only detect one type of ultraviolet light. Work diagram, mechanism of action, and photocurrent signal of p-AlGaN/n-GaN based PEC UV PD under different wavelengths. (Image: Wang et al.)

As reported in Advanced Photonic Nexus (“Structural design of photoelectrochemical photodetectors based on AlGaN/GaN nanowires: regulation of carrier transport in the GaN segment as a current flow center”), researchers from Nanjing Post and Telecommunications University (NJUPT) and Nanjing University recently designed a PEC UV PD that can detect two types of ultraviolet light by using a special type of nanostructure made of different layers.

This design makes the detector sensitive to changes in the environment, and the researchers can further improve the detector’s performance by modifying its surface. This new design offers a promising strategy for developing multifunctional optoelectronic devices.

The research team used aluminum gallium nitride (p-AlGaN/GaN) layered nanostructures as the electrodes in a three-electrode system to study how it detects light. They found that the tiny GaN semiconductor nanowires are critical in controlling the flow of electric current and reversing the direction of photocurrent in response to different types of light. They found that the nanowires act as a light absorber under 365 nm light while also functioning as an electron donor when exposed to 255 nm light, which helps regulate photoresponsiveness at various wavelengths.

The PEC UV PD design is able to discriminate between different wavelengths of light by using coated AlGaN/GaN nanowires instead of bare AlGaN nanowires, achieving a polarity reversal of the photocurrent at two different points. This makes it highly sensitive to changes in the surrounding environment, allowing easy adjustment of photo response via light intensity and external bias. In addition, by including platinum in the surface modification with PEC PD, the researchers were able to increase the photo response and achieve a very fast response speed of 20 ms at 255 nm light.

According to Dunjun Chen, professor of Electronic Science and Engineering and co-corresponding author of the work, “We focused on the importance of the GaN segment in these systems and showed how it affects the way the system transports energy.” Chen added, “This self-contained PEC photodetection system offers a new way to understand the transport mechanism in AlGaN/GaN nanowire PEC systems, which may lead to the development of more advanced optoelectronic devices in the future.”

This breakthrough highlights the potential for manipulating nanowire construction and surface dynamics to enhance the multifunctional performance of PEC PDs and could pave the way for more efficient and effective devices that can be used in a wide variety of applications.

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