JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, vol. 4, no. 3, page. 773 - 783, 2002-09
JOURNAL OF LUMINESCENCE, vol. 99, no. 1, page. 73 - 77, 2002-08
APPLIED PHYSICS LETTERS, vol. 79, no. 3, page. 326 - 328, 2001-07-16