Enhanced blue emission from Tm-doped AlxGa1−xN electroluminescent thin films

Electroluminescent (EL) emission from Tm-doped AlxGa1−xN (AlxGa1−xN:Tm) has been observed with various Al compositions (0⩽x⩽1). AlxGa1−xN:Tm thin films were grown by molecular beam epitaxy with in situ doping of Tm. At lower Al composition (x<0.15), blue emission at 478 nm dominates, corresponding to the Tm G41→H63 transition. For x>0.15, however, a second blue emission peak was observed at 465 nm, becoming dominant with increasing Al composition. The 465 nm emission is attributed to the higher level Tm transition D21→F43, which was not observed in GaN:Tm. Blue EL emission from Tm was enhanced with Al content in the films. The ratio of EL intensity at blue (465 nm plus 478 nm) to infrared (801 nm) wavelengths increased monotonically with Al composition, from ∼2 for GaN:Tm to ∼30 for AlN:Tm.