GaN/AlGaN solar-blind avalanche photodiodes (APDs) can enhance the AP Ds performance by using GaN instead of AlGaN as the multiplication layer due to the higher hole ionization coefficient in the GaN multiplication layer.While this APD can also absorb the radiation with energy larger than bandgap of GaN (λ <370nm) and therefore loses the solid-blind property.In this paper,the solar blind ultraviolet filter film with three periodic anti-reflect ion coatings between the basic films and air is designed by transfer matrix method,and the optical and electrical characteristics for heter o-structure GaN/AlGaN (APDs) integrated with this filter film on the back of the sapphire substrate are investigated by semiconduc tor device software Silvaco Atlas.The results show that the proposed filter film can increase pronouncedly the transmittance with λ<280nm and reflectivity in photonic bandgap. Therefore,the GaN/AlGaN APDs with designed filter film exhibit the smoother cur ve of spectral responsivity,the steeper cut-off edge and better filter performance compared with the GaN/AlGaN APDs using the fi lter film without anti-reflection coatings. Moreover,with respect to conventional AlGaN APDs,the GaN/AlGaN APDs facilitate s the photo-generated hole injection from absorption layer into multiplication layer,which enhances the maximum spectral responsivity and ultraviolet/visible rejection ratio of the GaN/AlGaN APDs over 300%