6 February 2012 Effect of dislocation density on efficiency curves in InGaN/GaN multiple quantum well light-emitting diodes
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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.
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Yoshiyuki Harada, Yoshiyuki Harada, Toshiki Hikosaka, Toshiki Hikosaka, Shigeya Kimura, Shigeya Kimura, Maki Sugai, Maki Sugai, Hajime Nago, Hajime Nago, Koichi Tachibana, Koichi Tachibana, Naoharu Sugiyama, Naoharu Sugiyama, Shinya Nunoue, Shinya Nunoue, } "Effect of dislocation density on efficiency curves in InGaN/GaN multiple quantum well light-emitting diodes", Proc. SPIE 8278, Light-Emitting Diodes: Materials, Devices, and Applications for Solid State Lighting XVI, 82780J (6 February 2012); doi: 10.1117/12.907679; https://doi.org/10.1117/12.907679

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