Selective enhancement of blue electroluminescence from GaN:Tm

Selective enhancement of electroluminescent emission from high-energy transitions in Tm-doped GaN has been observed to be a strong function of GaN growth temperature. GaN:Tm thin films have been grown by molecular beam epitaxy at temperatures from 100 to 700 degreesC. At low growth temperatures (100-200 degreesC) the low energy (infrared-801 nm) transition dominates, while at higher growth temperatures (400-700 degreesC) the high energy (blue-477 nm) transition dominates. For films grown at low temperatures the main emission excitation mechanism is impact excitation, while for films grown at higher temperatures (greater than or equal to600 degreesC) the main excitation mechanism appears to be lattice impact ionization followed by energy transfer to Tm ions. (C) 2003 American Institute of Physics.