Enhanced near-UV electroluminescence from p-GaN/i-Al2O3/n-ZnO heterojunction LEDs by optimizing the insulator thickness and introducing surface plasmons of Ag nanowires

Abstract

p-GaN/i-Al₂O₃/n-ZnO (PIN) heterojunction LEDs with different dielectric Al₂O₃ thicknesses were fabricated via an atomic layer deposition technique. By optimizing the i-Al₂O₃ layer thickness to be ∼12 nm, the effective electron accumulation and hole injection are simultaneously achieved in the n-ZnO active layer, resulting in a greatly improved near-UV electroluminescence intensity of this PIN type LED. Moreover, by introducing Ag nanowires, whose surface plasmon (SP) resonant energy is closer to the ZnO UV emission energy, into the LED structure, the electroluminescence intensity was further increased ∼2.8 times. Time-resolved and temperature-dependent spectroscopy analyses reveal that both the spontaneous radiation rate and internal quantum efficiency of the ZnO active layer are increased as a result of resonant couplings between ZnO excitons and Ag nanowire SPs, which gives rise to the observed near-UV electroluminescence enhancement.