Author Affiliations
Abstract
1 Institute of Micro-Nano Photoelectron and Electromagnetic Technology Innovation, School of Electronics and Information Engineering, Hebei University of Technology, Tianjin 300401, China
2 Key Laboratory of Electronic Materials and Devices of Tianjin, Tianjin 300401, China
3 State Key Laboratory of Solid-State Lighting, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
The tilted energy band in the multiple quantum wells (MQWs) arising from the polarization effect causes the quantum confined Stark effect (QCSE) for [0001] oriented III-nitride-based near ultraviolet light-emitting diodes (NUV LEDs). Here, we prove that the polarization effect in the MQWs for NUV LEDs can be self-screened once the polarization-induced bulk charges are employed by using the alloy-gradient InxGa1-xN quantum barriers. The numerical calculations demonstrate that the electric field in the quantum wells becomes weak and thereby flattens the energy band in the quantum wells, which accordingly increases the spatial overlap for the electron-hole wave functions. The polarization self-screening effect is further proven by observing the blueshift for the peak emission wavelength in the calculated and the measured emission spectra. Our results also indicate that for NUV LEDs with a small conduction band offset between the quantum well and the quantum barrier, the electron injection efficiency for the proposed structure becomes low. Therefore, we suggest doping the proposed quantum barrier structures with Mg dopants.
230.3670 Light-emitting diodes 230.5590 Quantum-well, -wire and -dot devices Chinese Optics Letters
2019, 17(12): 122301
Author Affiliations
Abstract
1 Institute of Micro-Nano Photoelectron and Electromagnetic Technology Innovation, School of Electronics and Information Engineering, Hebei University of Technology, Key Laboratory of Electronic Materials and Devices of Tianjin, Tianjin 300401, China
2 e-mail: zh.zhang@hebut.edu.cn
3 Department of Photonics and Institute of Electro-Optical Engineering, Taiwan Chiao Tung University, Hsinchu 30010, China
4 Department of Electrical Engineering and Computer Sciences and TBSI, University of California at Berkeley, Berkeley, California 94720, USA
It is well known that the p-type AlGaN electron blocking layer (p-EBL) can block hole injection for deep ultraviolet light-emitting diodes (DUV LEDs). The polarization induced electric field in the p-EBL for [0001] oriented DUV LEDs makes the holes less mobile and thus further decreases the hole injection capability. Fortunately, enhanced hole injection is doable by making holes lose less energy, and this is enabled by a specifically designed p-EBL structure that has a graded AlN composition. The proposed p-EBL can screen the polarization induced electric field in the p-EBL. As a result, holes will lose less energy after going through the proposed p-EBL, which correspondingly leads to the enhanced hole injection. Thus, an external quantum efficiency of 7.6% for the 275 nm DUV LED structure is obtained.
Photonics Research
2019, 7(4): 040000B1
