Abnormal Photocurrent in Semiconductor p‐n Heterojunctions: Toward Multifunctional Photoelectrochemical‐Type Photonic Devices and Beyond

Abstract

Semiconductor p‐n heterojunctions are important building blocks for modern electronic and photonic devices. Further combining semiconductor p‐n heterojunctions with light and electrolyte environment, interesting photoelectrochemical (PEC) phenomena can occur, which enriches the design principles of multifunctional devices. In fact, recent years have witnessed the emergence of PEC‐type photonic devices. For PEC‐type photonic devices, a key to realize multifunctionality is to control the photocurrent polarity of the photoelectrode. In this study, an abnormal photocurrent is reported from p‐InGaN/n‐GaN nanowire heterojunctions under a blue light illumination: although n‐GaN is transparent to the blue light (and thus optical absorption mainly occurs in p‐InGaN) and p‐InGaN in principle can only give negative PEC photocurrent, the detailed experiments show that positive PEC photocurrent can be generated from the p‐InGaN segment due to the existence of the built‐in electric field at the p‐n junction. This study shows a new route to control the photocurrent polarity in a semiconductor p‐n heterojunction photoelectrode. This unveiled role of the built‐in electric field is expected to impact the design of emerging PEC‐type photonic devices, as well as other novel photonic and electronic devices based on semiconductor nanowire p‐n heterojunctions.

Breaking the Built‐In Electric Field Barrier in p–n Heterojunction for Self‐Powered, Wavelength Distinguishable Photoelectrochemical Photodetectors: Toward Low Power Consumption and Secure Underwater Wireless Sensor Network

“…This is because the built-in electric field could have a photovoltaic (PV) effect similar to a solar cell, [26][27][28][29] i.e., upon light illumination on the p-side (whereas n-side remains transparent), the built-in electric field tends to separate the photogenerated electrons and holes near the p-n junction and sweep photogenerated electrons to n-side and photogenerated holes to p-side, making it difficult for HER to occur on the p-side and holes transport to the substrate. Although this could lead to abnormal photocurrent which might be favorable for certain applications, [30] this illustrates the generic difficulty of generating negative photocurrent in the working electrode with the n-down, p-up configuration in a 2-electrode PEC cell, which further limits the achievement of wavelength distinguishable light detection. This also means, in order to achieve wavelength-distinguishable light detection, improving the HER process on the working electrode is necessary.…”

Realizing Ultrafast Response Speed for Self-Powered Photodetectors with a Molecular-Doped Lateral InSe Homojunction

“…Superior photodetectors play a pivotal role in modern technology, spanning fields such as communication, information technology, and optoelectronics. − However, contemporary semiconductor photodetectors face a myriad of challenges in terms of high-speed response, sensitivity, and material selection, necessitating novel materials and structures to enhance device performance and meet the demands of future applications. , …”