Electroluminescence of ordered ZnO nanorod array/p-GaN light-emitting diodes with graphene current spreading layer.

Jing-Jing Dong,Hui-Ying Hao,Jie Xing,Zhen-Jun Fan,Zi-Li Zhang

doi:10.1186/1556-276x-9-630

Abstract

Ordered ZnO nanorod array/p-GaN heterojunction light-emitting diodes (LEDs) have been fabricated by introducing graphene as the current spreading layer, which exhibit improved electroluminescence performance by comparison to the LED using a conventional structure (indium-tin-oxide as the current spreading layer). In addition, by adjusting the diameter of ZnO nanorod array in use, the light emission of the ZnO nanorod array/p-GaN heterojunction LEDs was enhanced further. This work has great potential applications in solid-state lighting, high performance optoelectronic devices, and so on.PACS78.60.Fi; 85.60.Jb; 78.67.Lt; 81.10.Dn

Highlights

ZnO is regarded as one of the most promising semiconductor material for the application of ultraviolet lightemitting diodes (LEDs) due to its excellent optical and electrical properties, including a direct wide bandgap (3.37 eV) and a high exciton binding energy (60 meV) at room temperature
It can be seen that all the ZnO nanorod arrays reserve hexagonal periodicity and evenly distribution inheriting from the PS microsphere self-assembled monolayer (SAM), and the spacing between two neighboring nanorods is 500 nm which is predefined by the diameter of the PS microspheres
All of the ZnO nanorod arrays are hexagonal faceted perfectly aligned normal to the underlying substrate, indicating that each ZnO nanorod is a single crystal of wurtzite ZnO with growth direction along [0001]

Summary

Introduction

ZnO is regarded as one of the most promising semiconductor material for the application of ultraviolet lightemitting diodes (LEDs) due to its excellent optical and electrical properties, including a direct wide bandgap (3.37 eV) and a high exciton binding energy (60 meV) at room temperature. Ordered ZnO nanorod arrays, which have a lower defect density, an improvement in the light extraction efficiency of the LEDs, and a broadband suppression in reflection, are the most attractive [1,2,3,4,5]. By choosing an optimal diameter of the ZnO nanorod arrays, electroluminescence (EL) emission from the LED device can be enhanced further, because the waveguiding property of ZnO nanorods is closely related to the diameter [5,6]. The fabrication of ZnO nanorod array-based LEDs with a traditional indium-tin-oxide (ITO) current spreading layer is very complicated. Since ZnO nanorods do not form a continuous layer, it is necessary to protect the nanorods and isolate electrical contacts on the ZnO nanorods from

Methods

Results

Conclusion