Luminescence properties of highly Si-doped AlN

We report on the optical characterization of highly Si-doped AlN layers grown by plasma-assisted molecular-beam epitaxy. Cathodoluminescence spectra reveal a sharp band-edge line and two broadbands around 4.4 eV and 3.6 eV. Near-band-edge luminescence remains intense at room temperature, and shows a systematic redshift with increasing Si concentration. Regarding the low-energy bands, we observe a redshift of the emission around 3.6 eV with increasing Si concentration accompanied by an increase in relative intensity compared to the 4.4 eV band.