The present invention provides a filter with which
organic matter,
bacteria, viruses, and other harmful substances can be trapped, and the trapped material can be sterilized and decomposed, at low cost and extremely high efficiency. A porous
ceramic or
metal is used as a substrate, and a porous
semiconductor composed of a
semiconductor material having a light emitting function is formed in the interior or on the surface of this substrate. An
electrode is provided to this product to serve as a filter,
voltage is applied so that
ultraviolet light is emitted while a fluid is being filtered, and any harmful substances are filtered and simultaneously sterilized and decomposed. The porous
semiconductor layer is preferably composed of columns grown perpendicular to the substrate plane, and has the function of emitting
ultraviolet light with a
wavelength of 400 nm or less. The pores in the
porous substrate column are through-holes perpendicular to the substrate plane, and the
average size of these pores is preferably from 0.1 to 100 μm. The distal ends of the columns preferably have a pointed shape. To manufacture, a suspension of semiconductor particles having a light emitting function is filtered through the
porous substrate serving as a filter medium so as to form a deposited layer of semiconductor particles on the
porous substrate surface. A deposited layer of p-type semiconductor particles and a deposited layer of n-type semiconductor particles may also be formed so that these form a pn junction. Further, the present invention is characterized in that an insulating layer is formed on the top and bottom surfaces of the porous semiconductor layer, and semiconductor particles are dispersed in the insulating layer, with the bandgap of the semiconductor particles in the porous light emitting layer or the porous semiconductor layer being at least 3.2 eV, and being doped with
gadolinium, which is the light emitting center. In addition, the porous semiconductor layer may be made of
porous silicon nitride composed of columnar Si3N4 particles with an average
aspect ratio of at least 3 and an
oxide-based binder phase containing at least one of
rare earth element, and emit visible light or
ultraviolet light.