Researchers Realize the Control of Photocurrent Direction with Light

POSTED:2021-10-21

The direction of photocurrent in a p–n heterojunction device can be switched by using different wavelengths of light.

Semiconductor p-n junction, with its unique rectification behavior, acts as the fundamental building block to form numerous modern electronic components. Prominently, all of the p-n junction-based devices unexceptionally obey the basic semiconductor physics of unidirectional current flow that sometimes limits their functionalities to satisfy the versatile demands from the complex electronic world.

Combining with photoelectric effect, p-n junction has been used to build classical solid-state photodetectors for numerous photonic systems. However, their detection capability is fundamentally constrained to a certain spectrum range since they always generate photocurrent flows in the same direction (unipolar photoresponse).

With inspiration from earlier reports on novel p-n junction device architectures to expand the functionalities beyond a single p-n junction, in a study published in Nature Electronics, Prof. SUN Haiding and Prof. LONG Shibing from the University of Science and Technology of China proposed and demonstrated a new type of photodetector that the direction of photocurrent in a p–n heterojunction device can be switched by using different wavelengths of light, in other words, to create a dual-polar photoresponse that can be used for multi-bands or spectrally distinctive/selective photodetection.

Traditional p-n junction-based photodetectors generally show a unipolar photocurrent response when illuminated with light of wavelength equal or shorter than the optical bandgap of the materials. To overcome the limit, the team constructed a light-detection electrochemical cell based on p-AlGaN/n-GaN nanowire p-n heterojunction on conductive silicon substrate, and demonstrated distinctive photoresponse with reversed polarity from the cell under different illumination wavelength (e.g., 254 nm or 365 nm in this work for demonstration, as shorn in Figure 1). Essentially, they observed bidirectional photocurrent behavior after illumination of the device at two different wavelengths which triggered opposite redox reactions (hydrogen evolution reaction (HER) and oxygen evolution reaction (OER)) on the nanowire/electrolyte interface and thus induces polarity reverse of the photocurrent, as shown in Figure 2, enabling a fast and easy way to distinguish different spectral bands by simply verifying the polarity of photocurrent and its magnitude. In other words, this newly constructed light-detection electrochemical cell operates under a combination of physical processes (photoelectric conversion and carrier transport in single p-n junction) and chemical process (redox reaction on nanowire surface), enabling a fast and easy way to distinguish different spectral bands by simply verifying the polarity of photocurrent, which offers a new degree of freedom to manipulate the carrier transport and thus current flow in semiconductor devices.

Such bidirectional photocurrent behaviour could be used inapplications such as switchable light imaging and optical communication, as well as filter-less colour discrimination, especially in underwater or bio-related field since our device can be directly implemented in the aqueous condition without sophisticated packaging.

Paper link: https://www.nature.com/articles/s41928-021-00640-7

Figure 1: The working principle of the device

Figure 2: (a) the photocurrent density under 254 nm and 365 nm light illumination on the nanowire with and without Platinum decoration, showing the switch of photocurrent direction under different light irradiation. (b) the transmission electron microscopic image of our p-n heterojunction nanowires.  

Faculty Search

Friendly Links

Contact US

Address:Second Electrical Building,Western Campus of USTC

Post Code: 230026

Phone: (+86)-0551-63607041

Fax: (+86)-0551-63607041

E-mail: fansh@ustc.edu.cn