Underlying mechanism of blue emission enhancement in Au decorated p-GaN film

Localized surface plasmons (LSPs) excited on metallic structures often play a significant role in mediating the photoluminescence (PL) of semiconductors. For p-GaN film, due to the LSP coupling, blue emission was enhanced while defect-related green emission was quenched to noise level after the decoration with Au nanoparticles (NPs). Why could the Au SP in the green light region enhance the blue and even ultraviolet emission? In this paper, a series of near/far-field spectral analyses and simulations were conducted to understand this process. A clear physical model of LSP-induced electron transfer was proposed to explain the defect-related LSP generation, coupling, electron transfer, and further blue emission increase with green emission reduction. Based on the PL measurement, an insulating SiO2 layer was introduced to confirm the LSP-induced electron transfer between Au and GaN. Additional green light was introduced to observe the LSP-induced PL enhancement, in the same way as for samples with defects. Our study provides a full understanding of the mechanism of PL enhancement in Au decorated GaN and this model should be universal for similar metal/semiconductor systems.