Modeling of BDJ and BTJ structures for color detection

Two color-sensitive detectors, based respectively on BDJ and BTJ structures, have recently been developed in standard VLSI processes. The BDJ structure implemented in a CMOS process can produce two photocurrents, and the photocurrent ratio is a monotone function of the wavelength. The BTJ structure realized in a BiCMOS process gives three band-pass spectral response, thus allowing trichromatic color detection. In order to obtain better insight into the behavior of these two structures, and to simulate their characteristics, we have established physical models for photocurrent calculations. The following approach has been adopted: i) calculating drift and diffusion photocurrent components which are produced in different depletion layers and neutral regions of silicon; ii) according to their contributions, determining photocurrents flowing through each buried junction. A computer program can be written for device simulations. The validity of these models has been verified through comparison between simulations and measurements. These models can also be used to study effects of parameters involved in the presented models.