Enhanced ultraviolet electroluminescence and spectral narrowing from ZnO quantum dots/GaN heterojunction diodes by using high-k HfO2 electron blocking layer

We demonstrated the capability of realizing enhanced ZnO-related UV emissions by using the low-cost and solution-processable ZnO quantum dots (QDs) with the help of a high-k HfO2 electron blocking layer (EBL) for the ZnO QDs/p-GaN light-emitting diodes (LEDs). Full-width at half maximum of the LED devices was greatly decreased from similar to 110 to similar to 54 nm, and recombinations related to nonradiative centers were significantly suppressed with inserting HfO2 EBL. The electroluminescence of the ZnO QDs/HfO2/p-GaN LEDs demonstrated an interesting spectral narrowing effect with increasing HfO2 thickness. The Gaussian fitting revealed that the great enhancement of the Zn-i-related emission at similar to 414 nm whereas the deep suppression of the interfacial recombination at similar to 477 nm should be the main reason for the spectral narrowing effect. (c) 2014 AIP Publishing LLC.