Surface Plasmon Enhanced Hot Exciton Emission in Deep UV‐Emitting AlGaN Multiple Quantum Wells

The surface plasmon (SP)‐exciton coupling effect has attractive potential applications in nitride semiconductor‐based light‐emitting diodes (LEDs) with improved performances by enhancing the spontaneous radiative recombination rate, especially for AlGaN‐based deep UV LEDs with an intrinsic low internal quantum efficiency (IQE). In this work, significant deep UV emission enhancement is demonstrated on AlGaN‐based multiple quantum well (MQW) structure by introducing the coupling of local surface plasmons (LSPs) from Al nanoparticles (NPs) with the excitons in AlGaN MQWs. By precisely manipulating the size of the Al NPs, the evolution of emission wavelength and enhancement ratio for the SP‐coupled AlGaN MQWs along with the change of the LSP properties is investigated in detail. With respect to the bare MQWs, strong emission enhancements accompanied by large shifts towards shorter wavelengths are observed from the AlGaN MQW structure decorated with Al NPs, which is proposed to originate from the suppressing of the ground state exciton emission and the strongly enhanced emission from the high‐order QW exciton states by the LSP–exciton coupling process. Theoretical calculations confirm that the higher energy sub‐band e2–hh2 transition from the MQWs is the maximum enhanced emission channel through the SP coupling process.