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Proceedings Paper

Effect of dislocation density on efficiency curves in InGaN/GaN multiple quantum well light-emitting diodes
Author(s): Yoshiyuki Harada; Toshiki Hikosaka; Shigeya Kimura; Maki Sugai; Hajime Nago; Koichi Tachibana; Naoharu Sugiyama; Shinya Nunoue
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Paper Abstract

The contribution of reduction of threading dislocation densities (TDDs) to optical properties is investigated for InGaN/GaN light-emitting diodes (LEDs) grown on sapphire substrate. The external quantum efficiency (EQE) curves depending on the TDDs are discussed both theoretically and experimentally. At the current density of <20 A/cm2, the EQE increases with decreasing the edge-type TDD from 5 e8/cm2 to 2 e8/cm2. The current density at the maximum EQE shifts to lower value as the edge-type TDD decreases, whereas the EQE presents no remarkable difference in the highercurrent density range irrespective of the TDD. According to the rate equation (ABC) model, the peak shift reflects the Shockley-Read-Hall non-radiative process (A coefficient). Analysis of the photoluminescence (PL) decay and the dependence of integrated PL intensity on excitation power reveals that the threading dislocations act as non-radiative recombination centers in the multiple quantum well active region. The TDD of <2 e8/cm2 is required for highly efficient blue LEDs operating at current density of around 15 A/cm2, whereas the TDD of <5 e8/cm2 in required for the LEDs operating at around 50 A/cm2.

Paper Details

Date Published: 6 February 2012
PDF: 6 pages
Proc. SPIE 8278, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XVI, 82780J (6 February 2012); doi: 10.1117/12.907679
Show Author Affiliations
Yoshiyuki Harada, Toshiba Corp. (Japan)
Toshiki Hikosaka, Toshiba Corp. (Japan)
Shigeya Kimura, Toshiba Corp. (Japan)
Maki Sugai, Toshiba Corp. (Japan)
Hajime Nago, Toshiba Corp. (Japan)
Koichi Tachibana, Toshiba Corp. (Japan)
Naoharu Sugiyama, Toshiba Corp. (Japan)
Shinya Nunoue, Toshiba Corp. (Japan)

Published in SPIE Proceedings Vol. 8278:
Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XVI
Klaus P. Streubel; Heonsu Jeon; Li-Wei Tu; Norbert Linder, Editor(s)

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