Balancing the Photo-Induced Carrier Transport Behavior at Two Semiconductor Interfaces for Dual-Polarity Photodetection

The carrier transport dynamics at the surface/interface of semiconductors determine the electronic and optical properties of devices. Thus, precise control of their dynamic processes while understanding the nature of these characteristics is crucial for modulating device functionalities. Here, a photoelectrochemical-type photosensor is built using monocrystalline p-GaN nanowires on the Si platform, which unambiguously exhibits either positive or negative photocurrent upon different light illumination. Such dual-polarity photocurrents are attributed to photogenerated-carrier-transport competition at two interfaces: the GaN/electrolyte and GaN/Si interface. Particularly, a rational Pt decoration successfully accelerates the carrier migration at the GaN/electrolyte interface that breaks the original balance of carrier transport. This mechanism is further elaborated by Kelvin-probe-force-microscopy characterization, which intuitively reveals the impact of Pt decoration on modulating nanowires' surface band bending and the consequent carrier dynamics at the interfaces. These insights into the control of carrier dynamics shed light on achieving multi-functional PEC devices built upon simple semiconductor architectures.