On the Impact of Electron Leakage on the Efficiency Droop for AlGaN Based Deep Ultraviolet Light Emitting Diodes

Chunshuang Chu,Zi-Hui Zhang,Jiamang Che,Hua Shao,Hao-Chung Kuo,Yonghui Zhang,Kangkai Tian,Jianquan Kou

doi:10.1109/jphot.2020.2997343

Chunshuang Chu, Zi-Hui Zhang + Show 6 more

Open Access

https://doi.org/10.1109/jphot.2020.2997343

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Abstract

In this work, we have investigated the origin of efficiency droop for AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs). We find that the efficiency droop is likely to be caused by the electron leakage for DUV LEDs studied in this work. The electron leakage arises from the unbalanced electron and hole injection efficiencies. The correlation between the efficiency droop and the electron leakage can be numerically calculated by manipulating the conduction band barrier height of the p-AlGaN electron blocking layer (p-EBL) for the proposed DUV LEDs. For the purpose of demonstrating that the efficiency droop for DUV LEDs can be experimentally decreased by reducing the electron leakage, a p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -GaN/In0.15Ga0.85N/n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -GaN tunnel junction on DUV LED is grown by using metal organic chemical vapor deposition (MOCVD) technology. The tunnel junction helps to enhance the hole injection, thus decreasing the electron leakage and the efficiency droop. Moreover, the parasitic emission in the p-type hole injection layer is no longer observed thanks to the decreased electron leakage level.

Highlights

III-Nitride based light-emitting diodes (LEDs) are energy-saving, compact size and contaminationfree to the globe, and they can be applied to general lighting, light communication, UV curing etc [1]
In this work, we have investigated the origin of efficiency droop for AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs)
We can find that the efficiency droop increases from 5% to 83% with the affinity of p-AlGaN electron blocking layer (p-electron blocking layer (EBL)) varying from 3.30 eV to 3.40 eV for Device A

Summary

Introduction

III-Nitride based light-emitting diodes (LEDs) are energy-saving, compact size and contaminationfree to the globe, and they can be applied to general lighting, light communication, UV curing etc [1]. At the current stage, research effort has been invested to make AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) with high external quantum efficiency (EQE). Different methods have been proposed to reduce the electron leakage and the efficiency droop. The efficiency droop for EQE is observed for AlGaN-based DUV LEDs, which can be higher than 10% [17], [18]. The electron leakage is speculated to be the main cause for the efficiency droop by quantitatively analyzing all recombination rates for DUV LEDs [22]. We numerically and experimentally find that the electron leakage rather than the Auger recombination is responsible for the efficiency droop for DUV LEDs. The electron leakage is evidenced by observing the parasitic emission peak in the p-region. The parasitic emission vanishes for DUV LED with the tunnel junction, which further confirms that the efficiency droop arises from the electron leakage

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Results and Discussions

Conclusion