[1] Johnson E J, Kafalas J, Dyes W A 1982 Appl. Phys. Lett. 40 993
[2] Cho Y, Kim D S, Choe B, Lim H, Kim D 1997 Phys. Rev. B 56 R4375
[3] Zhang Y, Wang B, Liu X, Xiao M 2010 J. Appl. Phys. 107 103502
[4] Gong X, Chen W J 1998 Appl. Phys. Lett. 73 2875
[5] Yamashita S A,Ogawa N 1989 Phys.Status. Solidi B 118 89
[6] Matsuzawa T, Aoki Y, Takeuchi N, Maruyama Y 1996 J. Electrochem. Soc. 143 2670
[7] Kang C, Liu R, Chang J, Lee B 2003 Chem. Mater. 15 3966
[8] Lei B, Li B, Zhang H, Li W 2007 Opt. Mater. 29 1491
[9] Wang J X, Xie S S, Yuan H J, Yan X Q, Liu D F, Gao Y, Zhou Z P, Song L, Liu L F, Zhao X W, Dou X Y, Zhou W Y, Wang G 2004 Solid State Commun. 131 435
[10] Wang J X, Xie S S, Gao Y, Yan X Q, Liu D F, Yuan H J, Zhou Z P, Song L, Liu L F, Zhou W Y, Wang G 2004 J. Cryst. Growth. 267 177
[11] Zhang J C, Yu M H, Qin Q S 2010 J. Appl. Phys. 108 123518
[12] Zhang J C, Wang Y H, Zhang Z Y, Xie P, Li H H, Jiang Y P 2008 Chin. Lett. 25 1453
[13] Liao J S, Liu B, Lai H S 2009 J.Lumin. 129 668
[14] Yu M, Lin J, Fu J, Zhang H J, Han Y C 2003 J.Mater.Chem. 13 1413