Amplified Spontaneous Emission From ZnO in n-ZnO/p-GaN Heterojunction Light-Emitting Diodes With an External-Feedback Reflector

The effect of external feedback on the ultraviolet electroluminescence (EL) from n-ZnO/p-GaN heterojunction light-emitting diodes at room temperature was studied. Atomic layer deposition was used to grow the high-quality n-type ZnO epilayer, and the p-type GaN was prepared by metal-organic chemical vapor deposition on a double-polished c-Al₂O₃ substrate. The back of the c-Al₂O₃ substrate was deposited with aluminum as an external-feedback reflector. Significant enhancement of the EL intensity from ZnO, spectral narrowing, coupled with the superlinear increase in the ZnO EL intensity with the injection current have been observed, which are attributed to amplified spontaneous emission in the ZnO epilayer caused by the external optical feedback.