Blue–violet boron-based Distributed Bragg Reflectors for VCSEL application

BxGa1−xN layers as well as BxGa1−xN/GaN Distributed Bragg Reflector (DBR) structures were grown, for boron compositions between 0% and 1.3%, by Metal–Organic Vapour Phase Epitaxy. Refractive index, absorption coefficient and bandgap bowing of BxGa1−xN are extracted from a two-stage procedure based on spectroscopic ellipsometry and reflection measurements in the 250–850 nm range at room temperature. For all compositions of our BGaN alloys, we have obtained good agreement between experimental and simulated curves. It is shown that a large refractive index contrast between BGaN and GaN can be achieved for only 1% of boron. Moreover, the lattice mismatch between B0.01Ga0.99N and GaN is only 0.2%, which can lead to good structural quality of BGaN/GaN DBRs. Those properties can enable the development of innovative BGaN DBR technologies for Vertical Cavity Surface Emitting Lasers (VCSELs) in the blue–violet spectral range.