Photoluminescence properties of in situ Tm-doped AlxGa1−xN

We report on the photoluminescence (PL) properties of in situ Tm-doped AlxGa1−xN films (0⩽x⩽1) grown by solid-source molecular-beam epitaxy. It was found that the blue PL properties of AlxGa1−xN:Tm greatly change as a function of Al content. Under above-gap pumping, GaN:Tm exhibited a weak blue emission at ∼478 nm from the 1G4→3H6 transition of Tm3+. Upon increasing Al content, an enhancement of the blue PL at 478 nm was observed. In addition, an intense blue PL line appeared at ∼465 nm, which is assigned to the 1D2→3F4 transition of Tm3+. The overall blue PL intensity reached a maximum for x=0.62, with the 465 nm line dominating the visible PL spectrum. Under below-gap pumping, AlN:Tm also exhibited intense blue PL at 465 and 478 nm, as well as several other PL lines ranging from the ultraviolet to near-infrared. The Tm3+ PL from AlN:Tm was most likely excited through defect-related complexes in the AlN host.