Enhanced transfer efficiency of plasmonic hot-electron across Au/GaN interface by the piezo-phototronic effect

Abstract

Performances of plasmon-mediated optoelectronic devices are mainly limited by the transfer efficiency of the energetic hot electrons (QEHET) from metallic nanostructures into the semiconductor active region. Here, we report a novel strategy to enhance the efficiency of plasmon-induced hot-electron transfer (PHET) across Au nanoparticles (NPs)/GaN film via the external-strain-induced piezo-phototronic effect. By performing transient absorption (TA) spectrum measurement of the Au NPs/GaN freestanding membrane under different strain conditions, the enhancement of effective QEHET is estimated to be nearly 120% under 3.57% compressive straining. This enhancement is comparable or better than previously reported achievement using other methods such as controlling the material’s morphology or optimizing charge-transfer transition pathway. The mechanisms of the piezo-phototronic enhanced PHET rely on the modulated barrier height between Au NPs/GaN heterojunction. This was further confirmed by performing the photoresponse ability measurements in Au NPs/GaN film under external straining. Photoresponsivity of the plasmonic heterojunction is obviously increased/decreased when the hybrid membrane undergoes compressive/tensile strain. These results advance our understanding of the piezo-phototronic effect on QEHET in plasmonic heterostructures, and offer effective strategies to manipulate hot carrier dynamics for high-performance plasmonic devices and photoelectrochemical systems.