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

摘要

The carrier transport dynamics at the surface/interface of semiconductorsdetermine the electronic and optical properties of devices. Thus,precise control of their dynamic processes while understanding thenature of these characteristics is crucial for modulating device functionalities.Here, a photoelectrochemical-type photosensor is built usingmonocrystalline p-GaN nanowires on the Si platform, which unambiguouslyexhibits either positive or negative photocurrent upon different lightillumination. Such dual-polarity photocurrents are attributed to photogenerated-carrier-transport competition at two interfaces: the GaN/electrolyteand GaN/Si interface. Particularly, a rational Pt decoration successfullyaccelerates the carrier migration at the GaN/electrolyte interface thatbreaks the original balance of carrier transport. This mechanism is furtherelaborated by Kelvin-probe-force-microscopy characterization, whichintuitively 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 onachieving multi-functional PEC devices built upon simple semiconductorarchitectures.