Silicon UV flame detector utilizing photonic crystals

In this paper we propose a silicon UV flame detector for combustion systems. In gas burners the relative intensity of flame radiation is dominant in the UV region. In the visible and IR regions the relative intensity of radiation of the incandescent surfaces is several orders of magnitude greater than the gas flame radiation intensity. Therefore it is required that the flame detector has a much greater sensitivity in the UV region. The propose detector is formed on n-type silicon on isolator wafer. In order to suppress sensitivity in the visible and the IR regions, the absorption region of the detector is greatly reduced, and a UV filter utilizing photonic crystal is designed. The p-n junctions are formed by very shallow diffusion of impurities. The contacts are made after the deposition of a thin oxide layer. The UV filter is then sputtered on the detector surface. The filter consists of a thin silver film, and a 1D photonic crystal made of twelve pairs of NaF/Y2O3 layers. The photonic band gaps of the crystal should suppress the propagation of the light with wavelengths greater than 0.35 micrometers . For the detector active area of 5 mm2, the thickness of the silver layer of 0.13 micrometers and a dark current of 1 nA, the noise equivalent power at 0.32 micrometers is 4.23 10-13 W/Hz1/2. The calculated flame signal to total signal ratio is 0.52.