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Deep-UV distributed Bragg reflectors (DBRs) operating at λ = 220–250 nm with reflectivity close to unity were produced using epitaxial AlxGa1-xN/AlN superlattice structures grown on AlN/sapphire templates via metalorganic chemical vapor deposition. Owing to the near-bandedge excitonic resonance in the AlxGa1-xN layers, the AlN mole fractions, x, were regulated to keep the reflective plateau within the enhanced refractive index contrast region between AlGaN and AlN of approximately 7%–11%. For DBRs incorporating high-index layers of AlGaN grown via a flow-rate modulated epitaxy technique, a reflectivity of 97% was achieved with a total pair number of 30.5 which was much smaller than number of pairs needed for the DBRs with conventionally grown AlGaN layers. The stopbands of these DBRs were about 6–9 nm.

An optically pumped vertical-cavity surface-emitting laser with an electrically conducting n-type distributed Bragg reflector was achieved at 374.9 nm. An epitaxially grown 40-pair n-type AlGaN/GaN distributed Bragg reflector was used as the bottom mirror, while the top mirror was formed by a dielectric distributed Bragg reflector composed of seven pairs of HfO2/SiO2. A numerical simulation for the optical mode clearly demonstrated that a high confinement factor was achieved and the threshold pumping power density at room temperature was measured as 1.64 MW/cm2. The achieved optically pumped laser demonstrates the potential of utilizing an n-type distributed Bragg reflector for surface-emitting optical devices.

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