Enhanced electroluminescence using Ta_2O_5/ZnO/HfO_2 asymmetric double heterostructure in ZnO/GaN-based light emitting diodes

Abstract

ZnO/GaN-based light-emitting diodes (LEDs) with improved asymmetric double heterostructure of Ta₂O₅/ZnO/HfO₂ have been fabricated. Electroluminescence (EL) performance has been enhanced by the HfO₂ electron blocking layer and further improved by continuing inserting the Ta₂O₅ hole blocking layer. The origins of the emission have been identified, which indicated that the Ta₂O₅/ZnO/HfO₂ asymmetric structure could more effectively confine carriers in the active i-ZnO layer and meanwhile suppresses of radiation from GaN. This device exhibits superior stability in long-time running. It's hoped that the asymmetric double heterostructure may be helpful for the development of the future ZnO-based LEDs.