Dielectric Si O₂ Zr O₂ distributed Bragg reflectors for ZnO microcavities prepared by the reactive helicon-wave-excited-plasma sputtering method

Reactive helicon-wave-excited-plasma sputtering method is shown to be a suitable technique for the fabrication of high reflectivity (R) distributed Bragg reflectors (DBRs), in particular, operating at the resonance wavelength of B excitons in ZnO (366.5 nm), utilizing quarter-wavelength multilayers of Si O2 and Zr O2 dielectric films. According to the surface-damage-free nature and proper stoichiometry controllability of the method, dense dielectric films exhibiting ideal refractive indices (1.46 for Si O2 and 2.10 for Zr O2 at 633 nm) and small root-mean-square values for the surface roughness (0.20 nm for Si O2 and 0.53 nm for Zr O2) were deposited using Si and Zr targets and O2 gas at room temperature. Optical reflectance spectra of the Si O2 Zr O2 DBRs agreed with those calculated using the optical multilayer film theory, and eight-pair DBR exhibited R higher than 99.5% at 366.5 nm and 82 nm stop bandwidth (R95%). The results indicate that the DBR can be used for the realization of polariton lasers using ZnO microcavities.