AlN/AlGaN Bragg-Reflectors for UV Spectral Range Grown by Molecular Beam Epitaxy on Si (111)

Quarter-wave distributed Bragg reflectors (DBRs) consisting of AlN and AlxGa1-xN (x=0.25±3%) stacked layers designed for the UV spectral region have been grown on silicon substrates by molecular beam epitaxy. Transmission electron microscopy, Rutherford Back-Scattering and photoluminescence have been performed to assess the structural quality and the composition of DBRs. High reflectance values (91%) are obtained, for a relatively rather small number of periods (15), because of the larger refractive index ratio between AlN and AlGaN compared to traditional AlGaN/GaN DBRs. The experimental reflectance data were compared with calculations and show excellent agreement with respect to peak reflectance and spectral width.