Improved light extraction efficiency of GaN-based flip-chip light-emitting diodes with an antireflective interface layer

Dongxue Wu,Jinmin Li,Junxi Wang,Ping Ma,Shuo Zhang,Boting Liu

doi:10.1063/1.4948749

Abstract

GaN-based flip-chip light-emitting diodes (FC-LEDs) grown on nanopatterned sapphire substrates (NPSS) are fabricated using self-assembled SiO2 nanospheres as masks during inductively coupled plasma etching. By controlling the pattern spacing, epitaxial GaN can be grown from the top or bottom of patterns to obtain two different GaN/substrate interfaces. The optoelectronic characteristics of FC-LED chips with different GaN/sapphire interfaces are studied. The FC-LED with an antireflective interface layer consisting of a NPSS with GaN in the pattern spacings demonstrates better optical properties than the FC-LED with an interface embedded with air voids. Our study indicates that the two types of FC-LEDs grown on NPSS show higher crystal quality and improved electrical and optical characteristics compared with those of FC-LEDs grown on conventional planar sapphire substrates.

Highlights

At present, the use of nanopatterned sapphire substrates (NPSS) in epitaxial GaN growth technology has attracted considerable attention to achieve light-emitting diodes (LEDs) with high luminous efficiency.[1,2,3] Use of NPSS is an effective method to enhance both the internal quantum efficiency (IQE) by lower threading dislocation density[4,5,6,7] and light extraction efficiency (LEE) of LEDS.[8]
The flip-chip light-emitting diodes (FC-LEDs) with an antireflective interface layer consisting of a NPSS with GaN in the pattern spacings demonstrates better optical properties than the FC-LED with an interface embedded with air voids
Our study indicates that the two types of FC-LEDs grown on NPSS show higher crystal quality and improved electrical and optical characteristics compared with those of FC-LEDs grown on conventional planar sapphire substrates

Summary

Introduction

The use of nanopatterned sapphire substrates (NPSS) in epitaxial GaN growth technology has attracted considerable attention to achieve light-emitting diodes (LEDs) with high luminous efficiency.[1,2,3] Use of NPSS is an effective method to enhance both the internal quantum efficiency (IQE) by lower threading dislocation density[4,5,6,7] and light extraction efficiency (LEE) of LEDS.[8]. GaN-based flip-chip light-emitting diodes (FC-LEDs) grown on nanopatterned sapphire substrates (NPSS) are fabricated using self-assembled SiO2 nanospheres as masks during inductively coupled plasma etching.

Results

Conclusion