Blue, green and red emission from Ce3+, Tb3+ and Eu3+ ions in amorphous GaN and AlN thin films

We report strong blue. green and red emission from Ce3+, Tb3- and Eu3- ions, respectively. at room temperature in amorphous GaN and AIN thin films prepared by DC magnetron co-sputtering. We observe sharp characteristic emission peaks of intra-4f-shell transitions of the Tb3- ions (D-5(4) --> F-7(3,4,5,6) transitions) and Eu3- ions (D-5(0) --> F-7(1,2,3,4) transitions) and a strong but broad peak of 5d-4f emission from Ce3- ions over the temperature range 2-300 K. The photoluminescence decay time from the excited D-5(4) state of Tb3- ions in a-AIN is 1. 1 ms, which is similar to the radiative lifetime of this state in glasses. The broad photoluminescence peak centered at similar to400 nm in a-GaN shows a weak temperature dependence and may be attributed to the intrinsic tail-to-tail transitions in the amorphous matrix. The possible origin of the deep states. close to midgap in a-AIN, is briefly discussed. (C) 2002 Elsevier Science B.V. All rights reserved.