Image capture devices based on p–i–n silicon carbides for biometric applications

Abstract The laser scanned photodiode (LSP) image sensor is optimized and used as a biometric (fingerprint) reader. A laser light illuminates the fingerprint placed on a glass surface in front of the sensor. The reflecting light coming from the glass is projected onto the active surface. The image is converted directly into a proportional electric current using the LSP as fingerprint scanner. Results show that a trade-off between read-out parameters (fingerprint scanner) and the biometric sensing element structure (p–i–n structure) is needed to minimize the cross talk between the fingerprint ridges (dark regions) and the fingerprint valleys (illuminated regions). In the optimized configuration and under reverse bias the user-specific information minutiae present a good contrast and a spatial resolution of 20 μm . An increased light-to-dark sensitivity, a flux range of two orders of magnitude and a responsivity lower than 6.5 μW cm −2 were obtained under slightly reverse voltage.