author_facet Li, X.
Okur, S.
Zhang, F.
Avrutin, V.
Özgür, Ü.
Morkoç, H.
Hong, S. M.
Yen, S. H.
Hsu, T. C.
Matulionis, A.
Li, X.
Okur, S.
Zhang, F.
Avrutin, V.
Özgür, Ü.
Morkoç, H.
Hong, S. M.
Yen, S. H.
Hsu, T. C.
Matulionis, A.
author Li, X.
Okur, S.
Zhang, F.
Avrutin, V.
Özgür, Ü.
Morkoç, H.
Hong, S. M.
Yen, S. H.
Hsu, T. C.
Matulionis, A.
spellingShingle Li, X.
Okur, S.
Zhang, F.
Avrutin, V.
Özgür, Ü.
Morkoç, H.
Hong, S. M.
Yen, S. H.
Hsu, T. C.
Matulionis, A.
Journal of Applied Physics
Impact of active layer design on InGaN radiative recombination coefficient and LED performance
General Physics and Astronomy
author_sort li, x.
spelling Li, X. Okur, S. Zhang, F. Avrutin, V. Özgür, Ü. Morkoç, H. Hong, S. M. Yen, S. H. Hsu, T. C. Matulionis, A. 0021-8979 1089-7550 AIP Publishing General Physics and Astronomy http://dx.doi.org/10.1063/1.3699199 <jats:p>The relative roles of radiative and nonradiative processes and the polarization field on the light emission from blue (∼425 nm) InGaN light emitting diodes (LEDs) have been studied. Single and multiple double heterostructure (DH) designs have been investigated with multiple DH structures showing improved efficiencies. Experimental results supported by numerical simulations of injection dependent electron and hole wavefunction overlap and the corresponding radiative recombination coefficients suggest that increasing the effective active region thickness by employing multiple InGaN DH structures separated by thin and low barriers is promising for LEDs with high efficiency retention at high injection. The use of thin and low barriers is crucial to enhance carrier transport across the active region. Although increasing the single DH thickness from 3 to 6 nm improves the peak external quantum efficiency (EQE) by nearly 3.6 times due to increased density of states and increased emitting volume, the internal quantum efficiency (IQE) suffers a loss of nearly 30%. A further increase in the DH thickness to 9 and 11 nm results in a significantly slower rate of increase of EQE with current injection and lower peak EQE values presumably due to degradation of the InGaN material quality and reduced electron-hole spatial overlap. Increasing the number of 3 nm DH active regions separated by thin (3 nm) In0.06Ga0.94N barriers improves EQE, while maintaining high IQE (above 95% at a carrier concentration of 1018 cm−3) and showing negligible EQE degradation up to 550 A/cm2 in 400 × 400 μm2 devices due to increased emitting volume and high radiative recombination coefficients and high IQE. Time-resolved photoluminescence measurements revealed higher radiative recombination rates with increasing excitation due to screening of the internal field and enhanced electron and hole overlap at higher injection levels. To shed light on the experimental observations, the effect of free-carrier screening on the polarization field at different injection levels and the resulting impact on the quantum efficiency were investigated by numerical simulations.</jats:p> Impact of active layer design on InGaN radiative recombination coefficient and LED performance Journal of Applied Physics
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title Impact of active layer design on InGaN radiative recombination coefficient and LED performance
title_unstemmed Impact of active layer design on InGaN radiative recombination coefficient and LED performance
title_full Impact of active layer design on InGaN radiative recombination coefficient and LED performance
title_fullStr Impact of active layer design on InGaN radiative recombination coefficient and LED performance
title_full_unstemmed Impact of active layer design on InGaN radiative recombination coefficient and LED performance
title_short Impact of active layer design on InGaN radiative recombination coefficient and LED performance
title_sort impact of active layer design on ingan radiative recombination coefficient and led performance
topic General Physics and Astronomy
url http://dx.doi.org/10.1063/1.3699199
publishDate 2012
physical
description <jats:p>The relative roles of radiative and nonradiative processes and the polarization field on the light emission from blue (∼425 nm) InGaN light emitting diodes (LEDs) have been studied. Single and multiple double heterostructure (DH) designs have been investigated with multiple DH structures showing improved efficiencies. Experimental results supported by numerical simulations of injection dependent electron and hole wavefunction overlap and the corresponding radiative recombination coefficients suggest that increasing the effective active region thickness by employing multiple InGaN DH structures separated by thin and low barriers is promising for LEDs with high efficiency retention at high injection. The use of thin and low barriers is crucial to enhance carrier transport across the active region. Although increasing the single DH thickness from 3 to 6 nm improves the peak external quantum efficiency (EQE) by nearly 3.6 times due to increased density of states and increased emitting volume, the internal quantum efficiency (IQE) suffers a loss of nearly 30%. A further increase in the DH thickness to 9 and 11 nm results in a significantly slower rate of increase of EQE with current injection and lower peak EQE values presumably due to degradation of the InGaN material quality and reduced electron-hole spatial overlap. Increasing the number of 3 nm DH active regions separated by thin (3 nm) In0.06Ga0.94N barriers improves EQE, while maintaining high IQE (above 95% at a carrier concentration of 1018 cm−3) and showing negligible EQE degradation up to 550 A/cm2 in 400 × 400 μm2 devices due to increased emitting volume and high radiative recombination coefficients and high IQE. Time-resolved photoluminescence measurements revealed higher radiative recombination rates with increasing excitation due to screening of the internal field and enhanced electron and hole overlap at higher injection levels. To shed light on the experimental observations, the effect of free-carrier screening on the polarization field at different injection levels and the resulting impact on the quantum efficiency were investigated by numerical simulations.</jats:p>
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author Li, X., Okur, S., Zhang, F., Avrutin, V., Özgür, Ü., Morkoç, H., Hong, S. M., Yen, S. H., Hsu, T. C., Matulionis, A.
author_facet Li, X., Okur, S., Zhang, F., Avrutin, V., Özgür, Ü., Morkoç, H., Hong, S. M., Yen, S. H., Hsu, T. C., Matulionis, A., Li, X., Okur, S., Zhang, F., Avrutin, V., Özgür, Ü., Morkoç, H., Hong, S. M., Yen, S. H., Hsu, T. C., Matulionis, A.
author_sort li, x.
container_issue 6
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container_title Journal of Applied Physics
container_volume 111
description <jats:p>The relative roles of radiative and nonradiative processes and the polarization field on the light emission from blue (∼425 nm) InGaN light emitting diodes (LEDs) have been studied. Single and multiple double heterostructure (DH) designs have been investigated with multiple DH structures showing improved efficiencies. Experimental results supported by numerical simulations of injection dependent electron and hole wavefunction overlap and the corresponding radiative recombination coefficients suggest that increasing the effective active region thickness by employing multiple InGaN DH structures separated by thin and low barriers is promising for LEDs with high efficiency retention at high injection. The use of thin and low barriers is crucial to enhance carrier transport across the active region. Although increasing the single DH thickness from 3 to 6 nm improves the peak external quantum efficiency (EQE) by nearly 3.6 times due to increased density of states and increased emitting volume, the internal quantum efficiency (IQE) suffers a loss of nearly 30%. A further increase in the DH thickness to 9 and 11 nm results in a significantly slower rate of increase of EQE with current injection and lower peak EQE values presumably due to degradation of the InGaN material quality and reduced electron-hole spatial overlap. Increasing the number of 3 nm DH active regions separated by thin (3 nm) In0.06Ga0.94N barriers improves EQE, while maintaining high IQE (above 95% at a carrier concentration of 1018 cm−3) and showing negligible EQE degradation up to 550 A/cm2 in 400 × 400 μm2 devices due to increased emitting volume and high radiative recombination coefficients and high IQE. Time-resolved photoluminescence measurements revealed higher radiative recombination rates with increasing excitation due to screening of the internal field and enhanced electron and hole overlap at higher injection levels. To shed light on the experimental observations, the effect of free-carrier screening on the polarization field at different injection levels and the resulting impact on the quantum efficiency were investigated by numerical simulations.</jats:p>
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spelling Li, X. Okur, S. Zhang, F. Avrutin, V. Özgür, Ü. Morkoç, H. Hong, S. M. Yen, S. H. Hsu, T. C. Matulionis, A. 0021-8979 1089-7550 AIP Publishing General Physics and Astronomy http://dx.doi.org/10.1063/1.3699199 <jats:p>The relative roles of radiative and nonradiative processes and the polarization field on the light emission from blue (∼425 nm) InGaN light emitting diodes (LEDs) have been studied. Single and multiple double heterostructure (DH) designs have been investigated with multiple DH structures showing improved efficiencies. Experimental results supported by numerical simulations of injection dependent electron and hole wavefunction overlap and the corresponding radiative recombination coefficients suggest that increasing the effective active region thickness by employing multiple InGaN DH structures separated by thin and low barriers is promising for LEDs with high efficiency retention at high injection. The use of thin and low barriers is crucial to enhance carrier transport across the active region. Although increasing the single DH thickness from 3 to 6 nm improves the peak external quantum efficiency (EQE) by nearly 3.6 times due to increased density of states and increased emitting volume, the internal quantum efficiency (IQE) suffers a loss of nearly 30%. A further increase in the DH thickness to 9 and 11 nm results in a significantly slower rate of increase of EQE with current injection and lower peak EQE values presumably due to degradation of the InGaN material quality and reduced electron-hole spatial overlap. Increasing the number of 3 nm DH active regions separated by thin (3 nm) In0.06Ga0.94N barriers improves EQE, while maintaining high IQE (above 95% at a carrier concentration of 1018 cm−3) and showing negligible EQE degradation up to 550 A/cm2 in 400 × 400 μm2 devices due to increased emitting volume and high radiative recombination coefficients and high IQE. Time-resolved photoluminescence measurements revealed higher radiative recombination rates with increasing excitation due to screening of the internal field and enhanced electron and hole overlap at higher injection levels. To shed light on the experimental observations, the effect of free-carrier screening on the polarization field at different injection levels and the resulting impact on the quantum efficiency were investigated by numerical simulations.</jats:p> Impact of active layer design on InGaN radiative recombination coefficient and LED performance Journal of Applied Physics
spellingShingle Li, X., Okur, S., Zhang, F., Avrutin, V., Özgür, Ü., Morkoç, H., Hong, S. M., Yen, S. H., Hsu, T. C., Matulionis, A., Journal of Applied Physics, Impact of active layer design on InGaN radiative recombination coefficient and LED performance, General Physics and Astronomy
title Impact of active layer design on InGaN radiative recombination coefficient and LED performance
title_full Impact of active layer design on InGaN radiative recombination coefficient and LED performance
title_fullStr Impact of active layer design on InGaN radiative recombination coefficient and LED performance
title_full_unstemmed Impact of active layer design on InGaN radiative recombination coefficient and LED performance
title_short Impact of active layer design on InGaN radiative recombination coefficient and LED performance
title_sort impact of active layer design on ingan radiative recombination coefficient and led performance
title_unstemmed Impact of active layer design on InGaN radiative recombination coefficient and LED performance
topic General Physics and Astronomy
url http://dx.doi.org/10.1063/1.3699199