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

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. [ABSTRACT FROM AUTHOR]