Enhanced ultraviolet electroluminescence and spectral narrowing from ZnO quantum dots/GaN heterojunction diodes by using high-κ HfO_2 electron blocking layer

摘要

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-κ HfO_2 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 ～110 to ～54 nm, and recombinations related to nonradiative centers were significantly suppressed with inserting HfO_2 EBL. The electroluminescence of the ZnO QDs/HfO_2/p-GaN LEDs demonstrated an interesting spectral narrowing effect with increasing HfO_2 thickness. The Gaussian fitting revealed that the great enhancement of the Zn_i-related emission at ～414 nm whereas the deep suppression of the interfacial recombination at ～477 nm should be the main reason for the spectral narrowing effect.