Abstract
In this report, we locally modulate the doping type in the n-AlGaN layer by proposing n-AlGaN/p-AlGaN/n-AlGaN (NPN-AlGaN)-structured current spreading layer for AlGaN-based deep ultraviolet light-emitting diodes (DUV LEDs). After inserting a thin p-AlGaN layer into the n-AlGaN electron supplier layer, a conduction band barrier can be generated in the n-type electron supplier layer, which enables the modulation of the lateral current distribution in the p-type hole supplier layer for DUV LEDs. Additionally, according to our studies, the Mg doping concentration, the thickness, the AlN composition for the p-AlGaN insertion layer and the NPN-AlGaN junction number are found to have a great influence on the current spreading effect. A properly designed NPN-AlGaN current spreading layer can improve the optical output power, external quantum efficiency (EQE), and the wall-plug efficiency (WPE) for DUV LEDs.
Highlights
Owing to various applications such as disinfection, water purification, medical treatment, and high-density optical recording [1–8], intensive efforts have been invested for developing high-efficiency AlGaNbased deep ultraviolet light-emitting diodes (DUV Deep ultraviolet light-emitting diodes (LEDs))
Our results show that the lateral distribution for the holes can be homogenized by using the NPN-AlGaN junction, which enhances the optical output power, the external quantum efficiency, and the wall-plug efficiency for DUV LEDs
After comprehensive and systematic discussions, we find that the NPN-AlGaN junction can reduce the current crowding effect in the p-type hole supplier layer and improve the hole injection for DUV LEDs
Summary
Owing to various applications such as disinfection, water purification, medical treatment, and high-density optical recording [1–8], intensive efforts have been invested for developing high-efficiency AlGaNbased deep ultraviolet light-emitting diodes (DUV LEDs). DUV LEDs are operated by electrical bias, which is associated with current flow and carrier transport [11–13]. Another very important aspect regarding the current flow is the current crowding effect, which takes place when the device is biased at a very high current level [14]. DUV LEDs have a very inferior Mg doping efficiency in the p-AlGaN layer with high AlN component [15, 16], leading to low electrical conductivity. DUV LEDs adopt the flip-chip structures that feature the lateral injection scheme for the current. Compared to InGaN/GaNbased UV, blue and green LEDs, AlGaN-based DUV LEDs are more challenged by the current crowding effect [17]. The occurrence of the current crowding effect either at the p-contact electrode or at the
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