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Title: High-efficiency InGaN-based light-emitting diodes with nanoporous GaN:Mg structure

Abstract

In this research nanoporous structures on p-type GaN:Mg and n-type GaN:Si surfaces were fabricated through a photoelectrochemical (PEC) oxidation and an oxide-removing process. The photoluminescence (PL) intensities of GaN and InGaN/GaN multi-quantum-well (MQW) structures were enhanced by forming this nanoporous structure to increase light extraction efficiency. The PL emission peaks of an MQW active layer have a blueshift phenomenon from 465.5 nm (standard) to 456.0 nm (nanoporous) measured at 300 K which was caused by partially releasing the compressive strain from the top GaN:Mg layers. The internal quantum efficiency could be increased by a partial strain release that induces a lower piezoelectric field in the active layer. The thermal activation energy of a nanoporous structure (85 meV) is higher than the standard one (33 meV) from a temperature dependent PL measurement. The internal quantum efficiency and light extraction efficiency of an InGaN/GaN MQW active layer are significantly enhanced by this nanoporous GaN:Mg surface, and this PEC treated nanoporous structure is suitable for high-power lighting applications.

Authors:
; ; ; ; ; ; ;  [1];  [2];  [2]
  1. Department of Materials Engineering, National Chung Hsing University, Taichung, Taiwan (China)
  2. (China)
Publication Date:
OSTI Identifier:
20778693
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 88; Journal Issue: 8; Other Information: DOI: 10.1063/1.2178477; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ACTIVATION ENERGY; GALLIUM NITRIDES; INDIUM NITRIDES; LAYERS; LIGHT EMITTING DIODES; MAGNESIUM; MEV RANGE 10-100; OXIDATION; OXIDES; PHOTOLUMINESCENCE; PIEZOELECTRICITY; POROUS MATERIALS; QUANTUM EFFICIENCY; QUANTUM WELLS; SEMICONDUCTOR MATERIALS; SILICON; SPECTRAL SHIFT; STRAINS; TEMPERATURE DEPENDENCE; TEMPERATURE RANGE 0273-0400 K

Citation Formats

Lin Chiafeng, Zheng Jinghui, Yang Zhongjie, Dai Jingjie, Lin Deryuh, Chang Chungying, Lai Zhaoxu, Hong, C.S., Department of Electronic Engineering, National Changhua University of Education, Changhua, Taiwan, and Luxxon Technology Corporation, Shinwu Shiang, Taoyuan County. High-efficiency InGaN-based light-emitting diodes with nanoporous GaN:Mg structure. United States: N. p., 2006. Web. doi:10.1063/1.2178477.
Lin Chiafeng, Zheng Jinghui, Yang Zhongjie, Dai Jingjie, Lin Deryuh, Chang Chungying, Lai Zhaoxu, Hong, C.S., Department of Electronic Engineering, National Changhua University of Education, Changhua, Taiwan, & Luxxon Technology Corporation, Shinwu Shiang, Taoyuan County. High-efficiency InGaN-based light-emitting diodes with nanoporous GaN:Mg structure. United States. doi:10.1063/1.2178477.
Lin Chiafeng, Zheng Jinghui, Yang Zhongjie, Dai Jingjie, Lin Deryuh, Chang Chungying, Lai Zhaoxu, Hong, C.S., Department of Electronic Engineering, National Changhua University of Education, Changhua, Taiwan, and Luxxon Technology Corporation, Shinwu Shiang, Taoyuan County. Mon . "High-efficiency InGaN-based light-emitting diodes with nanoporous GaN:Mg structure". United States. doi:10.1063/1.2178477.
@article{osti_20778693,
title = {High-efficiency InGaN-based light-emitting diodes with nanoporous GaN:Mg structure},
author = {Lin Chiafeng and Zheng Jinghui and Yang Zhongjie and Dai Jingjie and Lin Deryuh and Chang Chungying and Lai Zhaoxu and Hong, C.S. and Department of Electronic Engineering, National Changhua University of Education, Changhua, Taiwan and Luxxon Technology Corporation, Shinwu Shiang, Taoyuan County},
abstractNote = {In this research nanoporous structures on p-type GaN:Mg and n-type GaN:Si surfaces were fabricated through a photoelectrochemical (PEC) oxidation and an oxide-removing process. The photoluminescence (PL) intensities of GaN and InGaN/GaN multi-quantum-well (MQW) structures were enhanced by forming this nanoporous structure to increase light extraction efficiency. The PL emission peaks of an MQW active layer have a blueshift phenomenon from 465.5 nm (standard) to 456.0 nm (nanoporous) measured at 300 K which was caused by partially releasing the compressive strain from the top GaN:Mg layers. The internal quantum efficiency could be increased by a partial strain release that induces a lower piezoelectric field in the active layer. The thermal activation energy of a nanoporous structure (85 meV) is higher than the standard one (33 meV) from a temperature dependent PL measurement. The internal quantum efficiency and light extraction efficiency of an InGaN/GaN MQW active layer are significantly enhanced by this nanoporous GaN:Mg surface, and this PEC treated nanoporous structure is suitable for high-power lighting applications.},
doi = {10.1063/1.2178477},
journal = {Applied Physics Letters},
number = 8,
volume = 88,
place = {United States},
year = {Mon Feb 20 00:00:00 EST 2006},
month = {Mon Feb 20 00:00:00 EST 2006}
}
  • InGaN-based light emitting diodes (LEDs) with a top pattern-nanoporous p-type GaN:Mg surface were fabricated by using a photoelectrochemical (PEC) process. The peak wavelengths of electroluminescence (EL) and operating voltages were measured as 461.2 nm (3.1 V), 459.6 nm (9.2 V), and 460.1 nm (3.3 V) for conventional, nanoporous, and pattern-nanoporous LEDs using 20 mA operation current. The EL spectrum of the nanoporous LED had a larger blueshift phenomenon as a result of a partial compression strain release in the InGaN active layer through the formation of a top nanoporous surface. The light output power had 12.1% and 26.4% enhancements formore » the nanoporous and the pattern-nanoporous LEDs compared with conventional LEDs. The larger operating voltage of the nanoporous LED was due to the non-ohmic contact on the PEC treated p-type GaN:Mg surface. By using a pattern-nanoporous p-type GaN:Mg structure, the operating voltage of the pattern-nanoporous LED was reduced to 3.3 V. A lower compression strain in the InGaN active layer and a higher light extraction efficiency at the top nanoporous surface were observed in pattern-nanoporous LEDs for higher efficiency nitride-based LED applications.« less
  • The efficiency droop of InGaN/GaN(InGaN) multiple quantum well (MQW) light emitting diodes (LEDs) with thin quantum barriers (QB) is studied. With thin GaN QB (3 nm–6 nm thickness), the efficiency droop is not improved, which indicates that hole transport cannot be significantly enhanced by the thin GaN QBs. On the contrary, the efficiency droop was remarkably reduced by using a InGaN staircase QB (InGaN SC-QB) MQWs structure where InGaN SC-QBs lower the transport energy barrier of holes. The efficiency droop ratio was as low as 3.3% up to 200 A/cm{sup 2} for the InGaN SC-QB LED. By using monitoring QW with longer wavelengthmore » we observe a much uniform carrier distribution in the InGaN SC-QB LEDs, which reveals the mechanism of improvement in the efficiency droop.« less
  • The spectra of electroluminescence, photoluminescence, and photocurrent for the In{sub 0.2}Ga{sub 0.8}N/GaN quantum-well structures are studied to clarify the causes for the reduction in quantum efficiency with increasing forward current. It is established that the quantum efficiency decreases as the emitting photon energy approaches the mobility edge in the In{sub 0.2}Ga{sub 0.8}N layer. The mobility edge determined from the photocurrent spectra is E{sub me} = 2.89 eV. At the photon energies hv > 2.69 eV, the charge carriers can tunnel to nonradiative recombination centers with a certain probability, and therefore, the quantum efficiency decreases. The tunnel injection into deep localizedmore » states provides the maximum electroluminescence efficiency. This effect is responsible for the origin of the characteristic maximum in the quantum efficiency of the emitting diodes at current densities much lower than the operating densities. Occupation of the deep localized states in the density-of-states 'tails' in InGaN plays a crucial role in the formation of the emission line as well. It is shown that the increase in the quantum efficiency and the 'red' shift of the photoluminescence spectra with the voltage correlate with the changes in the photocurrent and occur due to suppression of the separation of photogenerated carriers in the field of the space charge region and to their thermalization to deep local states.« less
  • The luminescence spectra, efficiency, and color characteristics of white-light-emitting diodes fabricated from p-n InGaN/AlGaN/GaN blue-light-emitting heterostructures grown on SiC substrates and coated with yellow-green phosphors based on the rare-earth-doped yttrium-aluminum garnets were studied. The efficiency of blue-emitting diodes is as high as 22% at a current of 350 mA and a voltage of 3.3 V. The white-emitting diodes have luminous efficiency as high as 40 lm/W and luminous flux up to 50 lm at 350 mA.
  • In this study, we demonstrated high efficiency InGaN/GaN light emitting diodes (LEDs) with asymmetric triangular multiple quantum wells (MQWs). Asymmetric triangular MQWs not only contribute to uniform carrier distribution in InGaN/GaN MQWs but also yield a low Auger recombination rate. In addition, asymmetric triangular MQWs with gallium face-oriented inclination band profiles can be immune from the polarization charge originating from typical c-plane InGaN/GaN quantum well structures. In the experiment, LEDs incorporated with asymmetric triangular MQWs with gallium face-oriented inclination band profiles exhibited a 60.0% external quantum efficiency at 20 mA and a 27.0% efficiency droop at 100 mA (corresponding to a currentmore » density of 69 A/cm{sup 2}), which accounted for an 11.7% efficiency improvement and a 31.1% droop reduction compared with symmetric square quantum well structure LEDs.« less