[1] Jung-Seung Yang, Hassanet Sodabanlu, Masakazu Sugiyama,Yoshiaki Nakano and Yukihiro Shimogaki, Appl. Phys. Lett.95, 162111(2009).
[2] Hai-Yan Zhu, Tong-Yi Zhang and Wei Zhao, J. Appl. Phys.105, 043518 (2009).
[3] P. K. Kandaswamy, H. Machhadani, C. Bougerol, S. Sakr, M. Tchernycheva, F. H. Julien and E. Monroy, Appl. Phys. Lett.95, 141911 (2009).
[4] M. Tonouchi, Nat. Photonics 197, 105 (2007).
[5] Yao Jian-Quan, Wang Jing-Li, Zhong Kai, Wang Ran, Xu De-Gang, Ding Xin, Zhang Fan and Wang Peng, Journal of Optoelectronics Laser 21, 1582 (2010). (in Chinese)
[6] Zhang Peng-Cheng, Qi Chang, Jiang Xian-Yang, Shi Xin-Zhi and Wang Gao-Feng, Journal of Optoelectronics Laser22, 1313 (2011). (in Chinese)
[7] B. S.Williams, Nat. Photonics 1, 517 (2007).
[8] M. A. Belkin, J. A. Fan, S. Hormoz, F. Capasso, S. P. Khanna, M. Lachab, A. G. Davies and E. H. Linfield, Opt. Express 16,3242 (2008).
[9] Y. Lu, X. Wang, L. Miao, D. Zuo and Z. Cheng, Appl. Phys.B 103, 387 (2011).
[10] K. L. Vodopyanov, M. M. Fejer, X. Yu, J. S. Harris, Y.-S. Lee, W. C. Hurlbut, V. G. Kozlov, D. Bliss and C. Lynch, Appl.Phys. Lett. 89, 141119 (2006).
[11] C. Sirtori, F. Capasso, J. Faist, L. N. Pfeiffer and K. W. West, Appl. Phys. Lett. 65, 445 (1994).
[12] Liu Dong-Feng, Lin Yi-Xin and Ma Cai-Hong, Semicond. Sci. Technol. 24, 045019 (2009).
[13] Berger Vincent, Semicond. Sci. Technol. 9, 1493 (1994).
[14] T. Hiroshima and R. Lang, Appl. Phys. Lett. 49, 456 (1986).
[15] Emmanuel Dupont, Zbig R.Wasilewski and H.C.Liu, IEEE Journal of Quantum Electronics 42, 1157 (2006).
[16] Nashun Wuritu and Gong Jian, Journal of Optoelectronics Laser 21, 1102 (2010). (in Chinese)