Browsing by Author "Li, Luping"

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Hole Transport Manipulation To Improve the Hole Injection for Deep Ultraviolet Light-Emitting Diodes
(2017-07-01)
Zhang, Zi-Hui
;
Chen, Sung-Wen Huang
;
Zhang, Yonghui
;
Li, Luping
;
Wang, Sheng-Wen
In this report, we propose to enhance the hole injection efficiency by adjusting the barrier height of the p-type electron blocking layer (p-EBL) for similar to 273 nm deep ultraviolet light-emitting diodes (DUV LEDs). The barrier height for the p-EBL is modified by employing a p-Al0.60Ga0.40N/Al0.50Ga0.50N/p-Al0.60Ga0.40N structure, in which the very thin Al0.50Ga0.50N layer is able to achieve a high local hole concentration, which is very effective in reducing the effective barrier height of the p-EBL for holes. More importantly, besides the thermionic emission, such a p-EBL structure can also favor a strong intraband tunneling process for holes. As a result, we can obtain a more efficient hole injection into the quantum wells, leading to a remarkably improved optical power for the DUV LED with the proposed p-EBL architecture.
On the Hole Injection for III-Nitride Based Deep Ultraviolet Light-Emitting Diodes
(2017-10-01)
Li, Luping
;
Zhang, Yonghui
;
Xu, Shu
;
Bi, Wengang
;
Zhang, Zi-Hui
The hole injection is one of the bottlenecks that strongly hinder the quantum efficiency and the optical power for deep ultraviolet light-emitting diodes (DUV LEDs) with the emission wavelength smaller than 360 nm. The hole injection efficiency for DUV LEDs is co-affected by the p-type ohmic contact, the p-type hole injection layer, the p-type electron blocking layer and the multiple quantum wells. In this report, we review a large diversity of advances that are currently adopted to increase the hole injection efficiency for DUV LEDs. Moreover, by disclosing the underlying device physics, the design strategies that we can follow have also been suggested to improve the hole injection for DUV LEDs.
UVA light-emitting diode grown on Si substrate with enhanced electron and hole injections
(2017-11-01)
Zhang, Zi-Hui
;
Chu, Chunshuang
;
Chiu, Ching Hsueh
;
Lu, Tien Chang
;
Li, Luping
In this work, III-nitride based similar to 370 nm UVA lightemitting diodes (LEDs) grown on Si substrates are demonstrated. We also reveal the impact of the AlN composition in the AlGaN quantum barrier on the carrier injection for the studied LEDs. We find that, by properly increasing the AlN composition, both the electron and hole concentrations in the multiple quantum wells (MQWs) are enhanced. We attribute the increased electron concentration to the better electron confinement within the MQW region when increasing the AlN composition for the AlGaN barrier. The improved hole concentration in the MQW region is ascribed to the reduced hole blocking effect by the p-type electron blocking layer (p-EBL). This is enabled by the reduced density of the polarization-induced positive charges at the AlGaN last quantum barrier (LB)/p-EBL interface, which correspondingly suppresses the hole depletion at the AlGaN LB/p-EBL interface and decreases the valence band barrier height for the p-EBL. As a result, the optical power is improved. (C) 2017 Optical Society of America