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 °C. At low growth temperatures (100–200 °C) the low energy (infrared-801 nm) transition dominates, while at higher growth temperatures (400–700 °C) 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 (⩾600 °C) the main excitation mechanism appears to be lattice impact ionization followed by energy transfer to Tm ions.