Zigzag and Helical AlN Layer Prepared by Glancing Angle Deposition and Its Application as a Buffer Layer in a GaN-Based Light-Emitting Diode

Lung-Chien Chen,Liu Xuguang,Xu Bingshe,Ching-Ho Tien

doi:10.1155/2012/409123

Abstract

This study investigates an aluminum nitride (AlN) nanorod structure sputtered by glancing angle deposition (GLAD) and its application as a buffer layer for GaN-based light-emitting diodes (LEDs) that are fabricated on sapphire substrates. The ray tracing method is adopted with a three-dimensional model in TracePro software. Simulation results indicate that the zigzag AlN nanorod structure is an optimal buffer layer in a GaN-based LED. Furthermore, the light output power of a GaN-based LED with a zigzag AlN nanorod structure improves to as much as 28.6% at a forward current of 20 mA over that of the GaN-based LED with a normal AlN buffer layer.

Highlights

The numerous applications of GaN-based light-emitting diodes (LEDs) include traffic lights, back light units in liquid crystal displays, indoor and outdoor lighting, street lighting, and exterior advertising displays
A 3 nm thick low-temperature grown GaN (LT-GaN), a 1 μm thick undoped GaN (U-GaN) layer, a 7 μm thick n-type GaN:Si (n-GaN) layer, 12 pairs of undoped InGaN/GaN multiplequantum wells, a 100 Athick Al0.01Ga0.99N:Mg layer, and a 0.3 μm thick GaN:Mg were grown sequentially on sapphire substrates with an aluminum nitride (AlN) nanorod structure as a buffer that had been prepared in advance by glancing angle deposition (GLAD) using metal-organic chemical vapor deposition (MOCVD)
The root mean square roughness of zigzag and helical AlN nanorod structures measured by atomic force microscopy is about 5.4 and 9.2 nm, respectively

Summary

Introduction

The numerous applications of GaN-based light-emitting diodes (LEDs) include traffic lights, back light units in liquid crystal displays, indoor and outdoor lighting, street lighting, and exterior advertising displays. As the conventional application in the recent decade, low-temperature GaN (LTGaN) buffer layers are inserted between the LED structure and substrate to increase the internal quantum efficiency of LEDs by improving the crystal quality of the LED structure [1,2,3,4]. In the structure of GaN-based LEDs, A1N has been applied between GaN epitaxial layer and sapphire substrate as a buffer layer to improve the quality of GaN epitaxial layer owing to a similar lattice constant with GaN [11,12,13]. By extending the results of previous efforts, this study investigates the zigzag and helical AlN nanorod structures that are prepared by GLAD [24]. This study investigates how the AlN nanorod structure affects the structural and optical characteristics of the GaN-based LED with zigzag and helical AlN nanorod structures

Experimental

Results and Discussion

Conclusions