Light extraction enhancement of ZnO-based heterojunction light-emitting diode with roughened-ZnO surface

Abstract

A hydrochloric acid (HCl)-etched ZnO surface was developed to enhance the light extraction efficiency (LEE) of the ZnO/GaN heterojunction light-emitting diodes (LEDs). This roughened surface led to the scattering of the incident light and resulted in the apparent enhancement of the film’s photoluminescence. It also showed better ohmic contact to the electrode ITO/Ag/ITO structure. The light output power density of the resulting LED was significantly higher than that of the referenced LED without the surface roughening process. Moreover, the roughened surface was beneficial for the current spreading of the injecting current. Accordingly, the luminance radiation from this device could be further optimized at an elevated injection current.