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Proceedings Paper

Low temperature studies of the efficiency droop in InGaN-based light-emitting diodes
Author(s): Jong-In Shim; Hyunsung Kim; Dong-Pyo Han; Dong-Soo Shin; Kyu Sang Kim
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Paper Abstract

The efficiency droop in light-emitting diodes (LEDs) represents a gradual decrease of the internal quantum efficiency (IQE) with increasing current. Experimentally, the IQE droops are strong functions of material, epitaxial and chip structures, and operating temperature. Recently, we have proposed an IQE droop model as the saturation of the radiative recombination rate at low current and subsequent increase in the nonradiative recombination rates at high current. Once the radiative recombination rate begins to saturate at an active region, the carrier density as well as the nonradiative recombination rate rapidly increase there. Eventually, the IQE droop appears from the increase in the nonradiative recombination rate being much larger than that in the radiative one. A dominant nonradiative recombination process is not solely determined for each LED chip, but it could vary with current level and operating temperature. As temperature decreases, in general, the IQE droop becomes larger with the peak IQE occurring at an extremely small current level. We test the droop model by investigating the radiative and nonradiative recombination processes separately from the cryogenic to room temperature. The characterization methods include comparative efficiency study between photoluminescence (PL) and electroluminescence (EL), open-circuit voltage under resonant PL excitation, interrelations of current-voltage-light characteristics, and EL spectra of color-coded quantum wells (QWs). Although a sudden increase of the nonradiative recombination rate is an apparent cause of the IQE droop, the saturation of the radiative recombination rate is the common trigger behind the IQE droop issue.

Paper Details

Date Published: 8 March 2014
PDF: 8 pages
Proc. SPIE 8986, Gallium Nitride Materials and Devices IX, 89861S (8 March 2014); doi: 10.1117/12.2037986
Show Author Affiliations
Jong-In Shim, Hanyang Univ. (Korea, Republic of)
Hyunsung Kim, Hanyang Univ. (Korea, Republic of)
Dong-Pyo Han, Hanyang Univ. (Korea, Republic of)
Dong-Soo Shin, Hanyang Univ. (Korea, Republic of)
Kyu Sang Kim, Sangji Univ. (Korea, Republic of)

Published in SPIE Proceedings Vol. 8986:
Gallium Nitride Materials and Devices IX
Jen-Inn Chyi; Yasushi Nanishi; Hadis Morkoç; Joachim Piprek; Euijoon Yoon; Hiroshi Fujioka, Editor(s)

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