Enhanced performance of InGaN/GaN multiple-quantum-well light-emitting diodes grown on nanoporous GaN layers.

Kwang Jae Lee,Kyungwook Hwang,Sang-Jo Kim,Seong-Ju Park,Jae-Joon Kim,Sung-Tae Kim

doi:10.1364/oe.22.0a1164

Kwang Jae Lee, Kyungwook Hwang + Show 4 more

Open Access

https://doi.org/10.1364/oe.22.0a1164

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Abstract

We demonstrate the high efficiency of InGaN/GaN multiple quantum wells (MQWs) light-emitting diode (LED) grown on the electrochemically etched nanoporous (NP) GaN. The photoluminescence (PL) and Raman spectra show that the LEDs with NP GaN have a strong carrier localization effect resulting from the relaxed strain and reduced defect density in MQWs. Also, the finite-difference time-domain (FDTD) simulation shows that the light extraction efficiency (LEE) is increased by light scattering effect by nanopores. The output power of LED with NP GaN is increased up to 123.1% at 20 mA, compared to that of LED without NP GaN. The outstanding performance of LEDs with NP GaN is attributed to the increased internal quantum efficiency (IQE) by the carrier localization in the indium-rich clusters, low defect density in MQWs, and increased LEE owing to the light scattering in NP GaN.

Highlights

GaN-based light-emitting diodes (LEDs) have been rapidly developed because of their tremendous potential for energy-efficient lighting and widespread LED applications
The optical performance of GaN-based LEDs still suffers from low internal quantum efficiency (IQE) and light extraction efficiency (LEE) [1,2,3,4,5]
These results show that the distribution of carrier localization states in multiple quantum wells (MQWs) is enhanced by the reduced strain in MQWs grown on the regrown NP GaN layer

Summary

Introduction

GaN-based light-emitting diodes (LEDs) have been rapidly developed because of their tremendous potential for energy-efficient lighting and widespread LED applications. The quantum confined Stark effect induced by the strong built-in piezoelectric field in InGaN/GaN multiple quantum wells (MQWs) lowers carrier recombination rate by increasing the spatial separation between the electron and hole wavefunctions [12]. Another important reason for the low EQE of such devices is their low LEE, which results from the total internal reflection of light emitted from MQWs because of the large difference in the refractive indices of GaN (n = 2.5) and air (n = 1) [13,14,15]. We reveal that the optical and electrical characteristics of LEDs can be improved by growth on a NP GaN layer

Experimental details

Results and discussion

Conclusion