A High-Performance SiO2/SiNx 1-D Photonic Crystal UV Filter Used for Solar-Blind Photodetectors

To improve the solar-blind/visible-blind photocurrent response rejection ratio of solar-blind photodetectors, we designed and fabricated a high-performance SiO
₂
/SiN
_x
1-D photonic crystal (PC) ultraviolet (UV) filter on (0 0 0 1) double-polished sapphire substrate. When depositing SiN
_x
, we found that employing NH3 as nitrogen precursor instead of N2 can simultaneously improve the peak reflectivity of filter stopband in the designed visible-blind region and the transmissivity in the solar-blind region. Research shows that it is associated with the H atom concentration in SiNx and the generation of Si-O-N transition layer at SiO
₂
/SiN
_x
interface. Finally, we obtained a high-performance SiO
₂
/SiN
_x
PC UV filter with a stopband reflectivity over 90% from 285 to 345 nm and a transmissivity over 80% in the solar-blind region. The UV filter is also demonstrated to have a good effect in improving the solar-blind/visible-blind photocurrent response rejection ratio of a back-illuminated AlGaN photodetector by depositing it to the back of the detector.