Research output per year
Research output per year
Ilya E. Titkov, Amit Yadav, Vera L. Zerova, Modestas Zulonas, Edik U. Rafailov, Sergey Yu. Karpov, Martin Strassburg, Ines Pietzonka, Hans-Juergen Lugauer, Bastian Galler
Research output: Chapter in Book/Published conference output › Conference publication
Internal quantum efficiency (IQE) of a high-brightness blue LED has been evaluated from the external quantum efficiency measured as a function of current at room temperature. Processing the data with a novel evaluation procedure based on the ABC-model, we have determined separately IQE of the LED structure and light extraction efficiency (LEE) of UX:3 chip.
Full text
Nowadays, understanding of LED efficiency behavior at high currents
is quite critical to find ways for further improvement of III-nitride LED performance
[1]. External quantum efficiency ηe
(EQE) provides integral information on the recombination and photon emission
processes in LEDs. Meanwhile EQE is the product of IQE ηi and LEE ηext at negligible carrier leakage from the active region.
Separate determination of IQE and LEE would be much more helpful, providing correlation
between these parameters and specific epi-structure and chip design. In this paper,
we extend the approach of [2,3] to the whole range of the current/optical power
variation, providing an express tool for separate evaluation of IQE and LEE.
We studied an InGaN-based LED fabricated by Osram OS. LED structure grown by MOCVD
on sapphire substrate was processed as UX:3 chip and mounted into the Golden Dragon
package without molding. EQE was measured with Labsphere CDS-600 spectrometer. Plotting
EQE versus output power P and finding the power Pm corresponding to EQE maximum
ηm enables comparing the measurements
with the analytical relationships ηi
= Q/(Q+p1/2+p-1/2) ,p = P/Pm , and Q = B/(AC) 1/2 where A, Band
C are recombination constants [4]. As a result, maximum IQE value equal to QI(Q+2)
can be found from the ratio ηm/ηe
plotted as a function of p1/2 +p1-1/2
(see Fig.la) and then LEE calculated as ηext
= ηm (Q+2)/Q . Experimental EQE as a function of normalized optical
power p is shown in Fig. 1 b along with
the analytical approximation based on the ABCmodel. The approximation fits perfectly
the measurements in the range of the optical power (or operating current) variation
by eight orders of magnitude.
In conclusion, new express method for separate evaluation of IQE and LEE of III-nitride
LEDs is suggested and applied to characterization of a high-brightness blue LED.
With this method, we obtained LEE from the free chip surface to the air as 69.8%
and IQE as 85.7% at the maximum and 65.2% at the operation current 350 rnA.
[I] G. Verzellesi, D. Saguatti, M. Meneghini, F. Bertazzi, M. Goano, G. Meneghesso, and E. Zanoni, "Efficiency droop in InGaN/GaN blue light-emitting diodes: Physical mechanisms and remedies," 1. AppL Phys., vol. 114, no. 7, pp. 071101, Aug., 2013.
[2] C. van Opdorp and G. W. 't Hooft, "Method for determining effective non radiative lifetime and leakage losses in double-heterostructure lasers," 1. AppL Phys., vol. 52, no. 6, pp. 3827-3839, Feb., 1981.
[3] M. Meneghini, N. Trivellin, G. Meneghesso, E. Zanoni, U. Zehnder, and B. Hahn, "A combined electro-optical method for the determination of the recombination parameters in InGaN-based light-emitting diodes," 1. AppL Phys., vol. 106, no. II, pp. 114508, Dec., 2009.
[4] Qi Dai, Qifeng Shan, ling Wang, S. Chhajed, laehee Cho, E. F. Schubert, M. H. Crawford, D. D. Koleske, Min-Ho Kim, and Yongjo Park, "Carrier recombination mechanisms and efficiency droop in GalnN/GaN light-emitting diodes," App/. Phys. Leu., vol. 97, no. 13, pp. 133507, Sept., 2010.
Original language | English |
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Title of host publication | Proceedings : 2014 international conference Laser Optics |
Place of Publication | Piscataway, NJ (US) |
Publisher | IEEE |
Number of pages | 1 |
ISBN (Electronic) | 978-1-4799-3885-8 |
ISBN (Print) | 978-1-4799-3884-1 |
DOIs | |
Publication status | Published - 31 Dec 2014 |
Event | 2014 international conference Laser Optics - St. Petersburg, Russian Federation Duration: 30 Jun 2014 → 4 Jul 2014 |
Name | 2014 International Conference Laser Optics |
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Conference | 2014 international conference Laser Optics |
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Abbreviated title | LO 2014 |
Country/Territory | Russian Federation |
City | St. Petersburg |
Period | 30/06/14 → 4/07/14 |
Research output: Chapter in Book/Published conference output › Conference publication
Research output: Chapter in Book/Published conference output › Conference publication
Research output: Chapter in Book/Published conference output › Conference publication