Design and fabrication of UV band-pass filters based on SiO2/Si3N4 dielectric distributed bragg reflectors

We have designed one kind of optical filters based on double stacks of 13.5-pairs SiO2/Si3N4 dielectric distributed Bragg reflector (DDBR) structures, to realize the passband with different central wavelengths in ultraviolet (UV) range. These SiO2/Si3N4 multi-layers have been successfully fabricated on (0001) sapphire substrates by plasma-enhanced chemical vapor deposition (PECVD). The reflectance spectra measured by the UV-visible spectrometer manifest that a series of band-pass filters with fixed passband width of similar to 30 nm and central passband varied from 310 nm to 370 nm have been obtained successfully. Besides, the other series of filters with passband width varied from 30 nm to 45 nm can be achieved. With good control of PECVD deposition parameters, all samples exhibit smooth surface with root mean square roughness less than 4.5 nm. Moreover, cross-section scanning electron microscope (SEM) images show these DDBR structures have good periodicity in accordance with the design, indicating that these band-pass filter structures are suitable for wavelength-window-selection UV photodetectors. (C) 2015 Elsevier B.V. All rights reserved.