[1] Nakamura S, Mukai T and M. Senoh 1994 Appl. Phys. Lett.
64 1687

[2] Mukai T, Narimatsu H and Nakamura S 1998 Jpn. J. Appl. Phys.
I$\!$I 37 L479

[3] Mukai T, Yamada M and Nakamura S 1998 Jpn. J. Appl.
Phys. I$\!$I 37 L1358

[4] Nakamura S, Mukai T, Senoh M and Iwasa N 1994 J. Appl.
Phys. 76 8189

[5] Tamura T, Setomoto T and Taguchi T 2000 J. Lumin. 87
1180

[6] Colvin V, Schlamp M and Alivisatos A 1994 Nature 370
354

[7] Adachi C, Baldo M A, Thompson M E and Forrest S R 2001 J.
Appl. Phys. 90 5048

[8] Lin J, Shi Y J and Yang Y 2001 Appl. Phys. Lett. 79 578

[9] Yang C H, Pan Y X and Zhang Q Y 2007 Mater. Sci. Eng. B
137 195

[10] Fu W T 1987 Mater. Res. Bull. 22 389

[11] Zhang Y and Yu L D 2004 J. Alloys Compd. 384 88

[12] Dieke G H 1968 Spectra and Energy Levels of Rare Earth Ions
in Crystal ed Crosswhite H M, Crosswhite H (New York:
Wiley-Interscience) p 142

[13] Guo F Y and Peng Y 1993 J. Inor. Chem. 9 177

[14] Huang S H and Lou L R 1990 Chin. J. Lumin. 11 1

[15] Dexter D L 1954 J. Chem. Phys. 22 1063