Controlled Mixed Violet−Blue−Red Electroluminescence from Eu:Nano-Phosphors/ZnO-Nanowires/p‑GaN Light-Emitting Diodes

Europium (Eu):Y2O3-nanoparticles/Mg:ZnO-nanowires/p-GaN and (Eu):chelate-based light-emitting diode (LED) structures have been fabricated, showing controlled mixed near-UV, violet, and red electroluminescence from trivalent europium. The magnesium (Mg)-doped ZnO (Mg:ZnO)-nanowires/p-GaN heterojunction were integrated into the LED structure and were covered on the top with the nanoparticle of yttrium oxide doped with trivalent europium ions (Eu3+:Y2O3) or by Eu:chelate. Samples exhibit mixed UV/blue light at ∼384 nm coming from the Mg:ZnO structure and a sharp red emission at ∼611 nm related to the intra4f transition of Eu ions. It is found that with Mg doping of ZnO, the emission wavelength of LEDs in the near-ultraviolet region is shifted to a smaller wavelength, thus being better adapted to the trivalent europium excitation band. Radiative energy transfer is achieved through the strong overlap between the emission wavelength from n-(Mg:ZnO)/p-GaN heterojunction and 7F0-5L6 absorption of Eu3+ ions in the...