Energy-Resolved Femtosecond Dynamics of Plasmon-Induced Hole Injection at Au/GaN Heterointerfaces.

Plasmon-induced interfacial hole injection at metal/semiconductor heterointerfaces represents a complementary pathway to conventional hot electron transfer, thereby broadening the functional landscape of plasmonic systems for energy conversion and optoelectronic technologies. However, direct experimental visualization of the energy-resolved femtosecond dynamics associated with this process remains elusive, as the intricate interfacial properties significantly complicate the underlying mechanism. Here, we reveal unprecedented spectral signatures of an ultrafast nonthermal hole transfer process at the Au/GaN heterointerface, occurring within 49 fs after plasmon excitation, on a timescale comparable to hot electron transfer. This process exhibits pronounced sensitivity to both excitation energy and light polarization, leading to a substantial reshaping of the low-energy electron distribution near the Fermi level by enhancing the low-energy electrons population and reducing the decay rate. Harnessing this ultrafast nonthermal hole transport results in a 14-fold enhancement in hydrogen evolution performance, demonstrating a promising approach for tailoring interfacial charge dynamics and offering mechanistic insights to guide the rational design of advanced plasmonic materials and device architectures.