[1] G.-c. Chen and G.-h. Fan, Optoelectronics Letters 10, 250 (2014).
[2] G. Lu, B. Wang and Y.-w. Ge, Optoelectronics Letters 11, 348 (2015).
[3] Y. Zhengmao, L. Xiaoyan, W. Huining, W. Yongzhong, H. Xiaopeng, J. Ziwu and X. Xiangang, Optics Express 21, 28531 (2013).
[4] J. Zhang, X.-J. Zhuo, D.-W. Li, Z.-W. Ren, H.-X. Yi, J.- H. Tong, X.-F. Wang, X. Chen, B.-J. Zhao and S.-T. Li, Superlattices and Microstructures 73, 145 (2014).
[5] Z.H. Zhang, W. Liu, Z. Ju, S.T. Tan, Y. Ji, Z. Kyaw, X. Zhang, L. Wang, X.W. Sun and H.V. Demir, Appl. Phys. Lett. 105, 033506 (2014).
[6] H.J. Li, J.J. Kang, P.P. Li, J. Ma, H. Wang, M. Liang, Z.C. Li, J. Li, X.Y. Yi and G.H. Wang, Appl. Phys. Lett. 102, 011105 (2013).
[7] Z.H. Zhang, W. Liu, S.T. Tan, Y. Ji, L. Wang, B. Zhu, Y. Zhang, S. Lu, X. Zhang and N. Hasanov, Appl. Phys. Lett. 105, 153503 (2014).
[8] L. Sun, G.-E. Weng, M.-M. Liang, L.-Y. Ying, X.-Q. Lv, J.-Y. Zhang and B.-P. Zhang, Physica E: Low- dimensional Systems and Nanostructures 60, 166 (2014).
[9] T. Fujii, Y. Gao, R. Sharma, E. Hu, S. DenBaars and S. Nakamura, Appl. Phys. Lett. 84, 855 (2004).
[10] T.-H. Lin, S.-J. Wang, Y.-C. Tu, C.-H. Hung, C.-A. Lin, Y.-C. Lin and Z.-S. You, Solid-State Electronics 107, 30 (2015).
[11] Y.C. Shen, J.J. Wierer, M.R. Krames, M.J. Ludowise, M.S. Misra, F. Ahmed, A.Y. Kim, G.O. Mueller, J.C. Bhat and S.A. Stockman, Proc. SPIE 5366, Light- Emitting Diodes: Research, Manufacturing, and Applications VIII, 20 (2004).
[12] C.-H. Liao, C.-Y. Chen, H.-S. Chen, K.-Y. Chen, W.-L. Chung, W.-M. Chang, J.-J. Huang, Y.-F. Yao, Y.-W. Kiang and C.-C. Yang, IEEE Photonics Technology Letters 23, 1757 (2011).
[13] S.-S. Schad, M. Scherer, M. Seyboth and V. Schwegler, Physica Status Solidi A Applied Research 188, 127 (2001).
[14] J.W. Lee, Y. Tak, J.Y. Kim, H.G. Hong, S. Chae, B. Min, H. Jeong, J. Yoo, J.R. Kim and Y. Park, J. Cryst. Growth 315, 263 (2011).
[15] APSYS, Crosslight Software Inc., Burnaby, Canada.
[16] M. Zhang, F. Yun, Y. Li, W. Ding, H. Wang, Y. Zhao, W. Zhang, M. Zheng, Z. Tian and X. Su, Physica Status Solidi 212, 954 (2015).
[17] L. Cheng, S. Wu, H. Chen, C. Xia and Q. Kong, Optical & Quantum Electronics 48, 1 (2016).
[18] E.F. Schubert, Light-emitting Diodes, Cambridge University Press, Cambridge, 2006.
[19] M. Suzuki, T. Uenoyama and A. Yanase, Physical Review B 52, 8132 (1995).