High-efficiency blue LEDs with thin AlGaN interlayers in InGaN/GaN MQWs grown on Si (111) substrates

Shigeya Kimura; Hisashi Yoshida; Toshihide Ito; Aoi Okada; Kenjiro Uesugi; Shinya Nunoue

doi:10.1117/12.2211880

26 February 2016 High-efficiency blue LEDs with thin AlGaN interlayers in InGaN/GaN MQWs grown on Si (111) substrates

Shigeya Kimura, Hisashi Yoshida, Toshihide Ito, Aoi Okada, Kenjiro Uesugi, Shinya Nunoue

Proceedings Volume 9748, Gallium Nitride Materials and Devices XI; 97481U (2016) https://doi.org/10.1117/12.2211880
Event: SPIE OPTO, 2016, San Francisco, California, United States

Abstract

We demonstrate high-efficiency blue light-emitting diodes (LEDs) with thin AlGaN interlayers in InGaN/GaN multiquantum wells (MQWs) grown on Si (111) substrates. The peak external quantum efficiency (EQE) η_EQE of 82% at room temperature and the hot/cold factor (HCF) of 94% have been obtained by using the functional thin AlGaN interlayers in the MQWs in addition to reducing threading dislocation densities (TDDs) in the blue LEDs. An HCF is defined as η_EQE(85°C)/η_EQE(25°C). The blue LED structures were grown by metal-organic chemical vapor deposition on Si (111) substrates. The MQWs applied as an active layer have 8- pairs of InGaN/Al_yGa_1-yN/GaN (0≤y≤1) heterostructures. Thinfilm LEDs were fabricated by removing the Si (111) substrates from the grown layers. It is observed by high-resolution transmission electron microscopy and three-dimensional atom probe analysis that the 1 nm-thick Al_yGa_1-yN interlayers, whose Al content is y=0.3 or less, are continuously formed. EQE and the HCFs of the LEDs with thin Al_0.15Ga_0.85N interlayers are enhanced compared with those of the samples without the interlayers in the low-current-density region. We consider that the enhancement is due to both the reduction of the nonradiative recombination centers and the increase of the radiative recombination rate mediated by the strain-induced hole carriers indicated by the simulation of the energy band diagram.

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Shigeya Kimura, Hisashi Yoshida, Toshihide Ito, Aoi Okada, Kenjiro Uesugi, and Shinya Nunoue "High-efficiency blue LEDs with thin AlGaN interlayers in InGaN/GaN MQWs grown on Si (111) substrates", Proc. SPIE 9748, Gallium Nitride Materials and Devices XI, 97481U (26 February 2016); https://doi.org/10.1117/12.2211880

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