Abstract
In this report, AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) with different p-AlGaN/n-AlGaN/p-AlGaN (PNP-AlGaN) structured current spreading layers have been described and investigated. According to our results, the adopted PNP-AlGaN structure can induce an energy barrier in the hole injection layer that can modulate the lateral current distribution. We also find that the current spreading effect can be strongly affected by the thickness, the doping concentration, the PNP loop, and the AlN composition for the inserted n-AlGaN layer. Therefore, if the PNP-AlGaN structure is properly designed, the forward voltage, the external quantum efficiency, the optical power, and the wall-plug efficiency for the proposed DUV LEDs can be significantly improved as compared with the conventional DUV LED without the PNP-AlGaN structure.
Highlights
Since the first occurrence in 2003, AlGaN-based deep ultraviolet light-emitting diodes (DUV Deep ultraviolet lightemitting diodes (LEDs)) have been attracting much interest due to their wide range of applications such as water sterilization and air purification [1,2,3,4,5,6,7]
To further address our point and for the purpose of the demonstration, we show the lateral hole concentration profile in the quantum well closest to the p-type Al0.60Ga0.40N electron blocking layer (p-EBL) [i.e., the last quantum well (LQW)] in Fig. 3b, which finds that the hole distribution in LED B shows a more uniform profile in the LQW
We find that by properly increasing the thickness, the doping concentration, the AlN composition for the n-AlGaN insertion layer, and the number for the PNP-AlGaN junction, the current spreading effect can be improved
Summary
Since the first occurrence in 2003, AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs) have been attracting much interest due to their wide range of applications such as water sterilization and air purification [1,2,3,4,5,6,7]. The external quantum efficiency (EQE) for DUV LEDs is lower than 10% when the emission wavelength is shorter than 300 nm [8], which significantly limits their further application. The low EQE partially arises from the poor internal quantum efficiency (IQE). AlGaN-based DUV LEDs that are grown on insulating sapphire substrates employ the flip-chip structure for the better light extraction efficiency. The flip-chip DUV LED structure requires the n-electrode and the p-electrode to be on the same side. Besides using the post-fabrication approaches, the current spreading layer can be obtained by in situ epitaxial growth in the metal-organic
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