Intersubband Transitions in Nonpolar GaN-based Resonant Phonon Depopulation Multiple-Quantum Wells for Terahertz Emissions

• Published in: Journal of the Korean Physical Society Vol. 74; no. 11; pp. 1039 - 1045
• Main Authors: Song, Ya-Feng, Kong, Xiong-Xiong, Tang, Wei-Bin, Suo, Zhong-Qiang, Zhang, Huan, Li, Chen-Yang, Jia, Qian, Xue, Cai-Xia, Lu, Yan-Wu, Yang, Chao-Pu
• Format: Journal Article
• Language: English
• Published: Seoul The Korean Physical Society 01.06.2019; Springer Nature B.V; 한국물리학회
• Subjects: Intersubband transitions; Mathematical and Computational Physics; Particle and Nuclear Physics; Phonons; Physics; Physics and Astronomy; Population decline; Population inversion; Quantum wells; Theoretical; Threshold currents; 물리학; Quantum cascade structures; Nonpolar GaN multiple-quantum well; Terahertz intersubband transitions; Resonant phonon depopulation
• ISSN: 0374-4884; 1976-8524
• DOI: 10.3938/jkps.74.1039

We investigate the polarization effect in intersubband transitions in polar and nonpolar GaN-based multiple-quantum well (MQW) structures for terahertz (THz) emissions by using systematic comparisons and design a nonpolar GaN/Al 0.2 Ga 0.8 N two-well-based MQW structure with an emitting photon of 7.27 THz (30.07 meV). Its lower energy separation (92.7 meV) matches the resonant phonon depopulation condition for better population inversion. It shows a lower threshold current density J th at all temperatures (1.548 kA/cm 2 at 90 K) and a higher output power of up to 86.1 mW at 5.8 K and 33.6 mW at 100 K. Our results for the polar GaN MQW are very close to the experimental data in the literature. We find that the J th of the nonpolar GaN MQW increases more slowly than that of the polar GaN MQW as temperature increases, indicating the nonpolar GaN MQW may be a worth-trying direction for improving the operation temperature. These results can provide meaningful references for the design and fabrication of nonpolar GaN-based THz MQW or quantum cascade structures.