Enhancement in Light Extraction Efficiency of GaN-Based Light-Emitting Diodes Using Double Dielectric Surface Passivation

Chung-Mo Yang,Yong Soo Lee,Jung-Hee Lee,Yun Soo Park,Jae-Hoon Lee,Dong-Seok Kim

doi:10.4236/opj.2012.23028

Abstract

SiO2Al2O3 double dielectric stack layer was deposited on the surface of the GaN-based light-emitting diode (LED). The double dielectric stack layer enhances both the electrical characteristics and the optical output power of the LED because the first Al2O3 layer plays a role of effectively passivating the p-GaN surface and the second lower index SiO2 layer increases the critical angle of the light emitted from the LED surface. In addition, the effect of the Fresnel reflection is also responsible for the enhancement in output power of the double dielectric passivated LED. The leakage current of the LED passivated with Al2O3 layer was -3.46 × 10-11 A at -5 V, at least two and three orders lower in magnitude compared to that passivated with SiO2 layer (-7.14 × 10-9 A) and that of non-passivated LED (-1.9 × 10-8 A), respectively, which indicates that the Al2O3 layer is very effective in passivating the exposed GaN surface after dry etch and hence reduces nonradiative recombination as well as reabsorption of the emitted light near the etched surface.

Highlights

The III-nitrides are suitable materials for photoelectronic applications covering most of the electromagnetic spectrum due to their wide range of direct bandgap energy
The leakage current of the Light-Emitting Diode (LED) passivated with Al2O3 layer was –3.46 × 10–11 A at –5 V, at least two and three orders lower in magnitude compared to that passivated with SiO2 layer (–7.14 × 10–9 A) and that of non-passivated LED (–1.9 × 10–8 A), respectively, which indicates that the Al2O3 layer is very effective in passivating the exposed GaN surface after dry etch and reduces nonradiative recombination as well as reabsorption of the emitted light near the etched surface
We report, in more detail, the development of passivation technique for the GaN-based LEDs by using double dielectric stack layer design is not optimized for the maximum anti-reflectivity

Summary

Introduction

The III-nitrides are suitable materials for photoelectronic applications covering most of the electromagnetic spectrum due to their wide range of direct bandgap energy. Surface passivation with appropriate dielectric layers is necessary to avoid non-radiative recombination for high ηrad [2]. Special techniques such as control of surface roughness [3,4,5], preparation of patterned sapphire substrate (PSS) [6,7], application of flip-chip bonding [8,9,10], adaption of laser lift-off process [11], and formation of photonic crystal structure [12] are frequently used to improve ηext, which can be increased by increasing the critical angle for the emitted light through an appropriate modification of the surface of the LED [13,14]. We report, in more detail, the development of passivation technique for the GaN-based LEDs by using double dielectric stack layer design is not optimized for the maximum anti-reflectivity

Device Fabrication

Optimization of Double Dielectric Stack Layer

Results and Discussion

R n GaN n GaN nair nair

Conclusion