Optical Performance of Top-Down Fabricated AlGaN Nanorod Arrays with Multi-Quantum Wells Embedded

Shucheng Ge,Youdou Zheng,Jiangping Dai,Kai Huang,Penggang Li,Na Gao,Rong Zhang,Shiqiang Lu,Junyong Kang,Bin Liu

doi:10.1186/s11671-019-3003-1

Abstract

Deep ultraviolet AlGaN-based nanorod (NR) arrays were fabricated by nanoimprint lithography and top-down dry etching techniques from a fully structural LED wafer. Highly ordered periodic structural properties and morphology were confirmed by scanning electron microscopy and transmission electron microscopy. Compared with planar samples, cathodoluminescence measurement revealed that NR samples showed 1.92-fold light extraction efficiency (LEE) enhancement and a 12.2-fold internal quantum efficiency (IQE) enhancement for the emission from multi-quantum wells at approximately 277 nm. The LEE enhancement can be attributed to the well-fabricated nanostructured interface between the air and the epilayers. Moreover, the reduced quantum-confined stark effect accounted for the great enhancement in IQE.

Highlights

In the past decade, AlGaN-based UV LEDs have attracted wide attention because of their promising applications such as water purification, sterilization, and biochemical detection. [1–3]
Strong piezoelectric field exists in the AlGaN multi-quantum wells (MQWs), resulting in spatial separation of electrons and holes, named as quantum-confined stark effect (QCSE), which dramatically decreases the internal quantum efficiency (IQE) [4]
In summary, highly uniform AlGaN NR arrays with MQWs embedded have been successfully fabricated by nanoimprint lithography (NIL) and top-down etching techniques

Summary

Introduction

AlGaN-based UV LEDs have attracted wide attention because of their promising applications such as water purification, sterilization, and biochemical detection. [1–3]. Strong piezoelectric field exists in the AlGaN multi-quantum wells (MQWs), resulting in spatial separation of electrons and holes, named as quantum-confined stark effect (QCSE), which dramatically decreases the internal quantum efficiency (IQE) [4]. Another problem is the low light extraction efficiency (LEE) [5], which is caused by the internal total reflection at the epilayers’ interface, and by the dominant transverse magnetic (TM) polarized light [6]. The interface engineering, such as incorporating structures like photonic crystal [8, 9], patterned substrate [10, 11], distributed Bragg Reflector [12], and surface plasmons [13–16], can enhance the LEE of the deep UV LEDs. the combination of these methods is relatively difficult

Methods

Results

Conclusion