Abstract
In this work, we numerically investigate the N-polar AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) over the Ga-polar DUV LEDs. The light output power has increased from 7.1 mW of Ga-polar DUV LED to 18.8 mW of N-polar DUV LED at 60 mA, and the wall-plug efficiency (WPE) of N-polar DUV LED is boosted by 104% at 60 mA with the same structure of Ga-polar conventional DUV LED. Furthermore, the higher operation voltage of N-polar DUV LED induced by the large energy difference between the p-type interlayer and the p-GaN hole supplier is noted. To reduce the operation voltage of N-polar DUV LED, the structure with a staircase-like p-type interlayer is proposed. The incorporation of staircase-like aluminum composition p-type interlayer mitigates the large potential barrier for holes injection, and the operation voltage is comparable to the Ga-polar DUV LED. The reduced operation voltage further promotes the WPE of N-polar DUV LEDs. Thus, combined with the promoted electron blocking ability and the mitigated potential barrier for holes of N-polar DUV LED, the greatly enhanced WPE is as high as 4.9% at 60 mA, which is 2.88 times higher than the Ga-polar DUV LED.
Highlights
AlGaN-based deep ultraviolet light-emitting diodes (DUV Light-emitting diodes (LEDs)) are deemed as the most promising candidate for environment-friendly DUV light sources [1]–[3]
Based on the reference Ga-polar DUV LED structure, we investigate the N-polar DUV LED to probe the polarity effect, which is denoted as Device B here
The simulation results of N-polar conventional DUV LED reveal its superior capability for blocking electrons due to the enhanced electron barrier of electron blocking layer (EBL)
Summary
AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) are deemed as the most promising candidate for environment-friendly DUV light sources [1]–[3]. The external quantum efficiency co-affected by both the IQE and LEE deteriorates [16] These technical challenges severely hinder the progress to fully replace the conventional mercury-based UV light sources. Carrier transport of DUV LEDs is very sensitive to the energy band structure of the electron blocking layer (EBL) and multiple quantum wells (MQWs) [19], [20]. It is found that N-polar DUV LED greatly enhances the light output power and WPE. A new staircase-like p-type AlGaN interlayer structure is proposed to mitigate the high operation voltage of N-polar DUV LEDs. In the staircase-like p-AlGaN interlayer, the Al composition is 60%, 50%, 40%, 30%, and 20% along [000-1] direction sequentially, each layer is 10 nm thick. The mitigated operation voltage confirms the new structure is favorable for WPE further promotion
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