Hot-Hole versus Hot-Electron Transport at Cu/GaN Heterojunction Interfaces

Abstract

Among all plasmonic metals, copper (Cu) has the greatest potential for realizing optoelectronic and photochemical hot-carrier devices, thanks to its CMOS compatibility and outstanding catalytic properties. Yet, relative to gold (Au) or silver (Ag), Cu has rarely been studied and the fundamental properties of its photoexcited hot carriers are not well understood. Here, we demonstrate that Cu nanoantennas on p-type gallium nitride (p-GaN) enables hot-hole-driven photodetection across the visible spectrum. Importantly, we combine experimental measurements of the internal quantum efficiency (IQE) with ab initio theoretical modelling to clarify the competing roles of hot-carrier energy and mean-free path on the performance of hot-hole devices above and below the interband threshold of the metal. We also examine Cu-based plasmonic photodetectors on corresponding n-type GaN substrates that operate via the collection of hot electrons. By comparing hot hole and hot-electron photodetectors that employ the same metal/semiconductor interface (Cu/GaN), we further elucidate the relative advantages and limitations of these complementary plasmonic systems. In particular, we find that harnessing hot holes with p-type semiconductors is a promising strategy for plasmon-driven photodetection across the visible and ultraviolet regimes. Given the technological relevance of Cu and the fundamental insights provided by our combined experimental and theoretical approach, we anticipate that our studies will have a broad impact on the design of hot-carrier optoelectronic devices and plasmon-driven photocatalytic systems.

In Situ Visualization of Localized Surface Plasmon Resonance‐Driven Hot Hole Flux

“…However, the short lifetime ( t <10 ps) and mean‐free path ( l mfp ≈ 5–10 nm) of hot holes compared to hot electrons impose an obstacle to harnessing their positive characteristics. [ 10,14 ] As a result, relatively few studies on hot holes from plasmonic metal have been conducted either by theoretical simulations or by experimentally measuring the averaged hot hole flux in the target area, [ 14,35–39 ] despite the marvelous potential for next‐generation applications; this is in sharp contrast to the research on hot electron collection and conversion. [ 2,4–6,12,15–17,22,23,25,26,30,32,34,40 ] Furthermore, local observation of plasmonic hot holes at the nanoscale has not been demonstrated, in spite of its importance of fundamental understanding of hot carrier physics.…”

Progress of GaN‐Based Optoelectronic Devices Integrated with Optical Resonances

“…Hot hole and electron excitation in GaN-SP coupling systems have been reported in a serial of recent works. [55][56][57] Duchene et al proposed a plasmonic Au/p-GaN photocathode as a hot hole generator for CO 2 reduction in 2018. [58] The proposed photocathode is able to collect hot holes at least 1.1 eV below Au Fermi level.…”

“…Hot hole and electron excitation in GaN‐SP coupling systems have been reported in a serial of recent works. [ 55–57 ] Duchene et al. proposed a plasmonic Au/p‐GaN photocathode as a hot hole generator for CO 2 reduction in 2018.…”

Hot hole transfer from Ag nanoparticles to multiferroic YMn2O5 nanowires enables superior photocatalytic activity

“…The harvesting of hot holes in such plasmon-semiconductor heterojunctions is relatively rare [33][34][35] in comparison to the large number of reports on successful hot electron harvesting in junctions between n-type semiconductors and coinage metals. One major engineering problem is the difficulty in achieving high performance Schottky barriers between p-type semiconductors and high work function coinage metals.…”