A study of the spectral sensitivity of photodiode from a standard CMOS process for DNA detection

The spectral sensitivity of junction photodiode used for detecting labeled DNA sample in genomic engineering field has been studied. From the theoretical point of view, the most important factors that determine sensitive range of junction photodiode are absorption coefficient, index of reflection coefficient and spectral density of the signal. Based on these three factors, the spectral sensitivities of commonly used junction photodiodes are presented. A silicon junction photodiode has been used to detect DNA samples with an optical label Texred. The spectral response of CMOS based photodiode to the optical spectrum related to the emissions of DNA optical label with different UV light excitation sources are studied. It is found that by adjusting the light source spectrum, the spectral response of the photodiode can be used as a natural filter to detect the desired signal. This approach can significantly simplify the fabrication of integrated detection system for biochip applications