[1] [1] L. Tang, H. P. Xia, P. Y. Wang, J. T. Peng, and H. C. Jiang, Chin. Opt. Lett. 11, 061603 (2013).

[2] [2] P. Xu, C. T. Xia, F. Wu, X. Li, Q. L. Sai, G. Q. Zhou, and X. D. Xu, Chin. Opt. Lett. 10, 021601 (2012).

[3] [3] S. Nakamura, MRS Bull. 22, 29 (1997).

[4] [4] S. Nakamura and G. Fasol, The Blue Laser Diode: GaN Based Light Emitters and Lasers (Springer, Berlin, 1997), p. 317.

[5] [5] P. L. Li, Y. S. Wang, S. L. Zhao, F. J. Zhang, and Z Xu, Chin. Phys. B 21, 127804 (2012).

[6] [6] Q. Su, Z. Pei, L. Chi, H. Zhang, Z. Zhang, and F. Zou, J. Alloys Compounds 192, 25 (1993).

[7] [7] Q. Zhang, C. Guo, C. Shi, S.-Z. Lü, J. Alloys Compounds 309, 10 (2000).

[8] [8] Q. Wang, Y. Li, Z. Zeng, and S. Pang, J Nanopart Res. 14, 1076 (2012).

[9] [9] S. Neeraj, N. Kijima, and A. K. Cheetham, Chem. Phys. Lett. 387, 2 (2004).

[10] [10] S. Tokunaga, H. Kato, and A. Kudo, Chem. Mater. 13, 4624 (2001).

[11] [11] Y. Wang, S. Wang, Z. Wu, W Li, and Y Ruan, J. Alloys Com-pounds 551, 262 (2013).

[12] [12] A. Hagfeldt and M. Gratzel, Chem. Rev. 95, 49 (1995).

[13] [13] G. Blasse and A. Bril, J. Chem. Phys. 48, 217 (1968).

[14] [14] S. Neeraj, N. Kijima, A. K. Chetham, Solid State Commun. 131, 65 (2004).

[15] [15] M. Yu, J. Lin, Z. Zhang, J. Fu, S. Wang, H. J. Zhang, and Y. C. Han, Chem. Mater. 14, 2224 (2002).

[16] [16] Q. Dou, Y. Zhang, ACS Publ. 27, 13236 (2011).

[17] [17] J.S. Yoo, and J. D. Lee, J. Appl. Phys. 81, 2810 (1997).