Single- and dual-axis lateral photodetectors of rectangular shape

A 2-dimensional diffusion model of rectagular single-and dual-axis, lateral photodiodes is analyzed and the different underlying lateral effects are discussed for the small-signal (unbiased) and fully reverse-biased modes, with either infinite terminating impedances at midlateral point contacts or zero loading impedances at extended lateral contacts. For the single-axis detector with two opposite extended contacts, previous results of the 1-dimensional model appear to remain valid, and the output current difference to sum ratio in the fully reverse-biased mode is a linear function of the position of a narrow incident light beam. For the dual-axis detector with extended contacts at all four sides--except for small gaps at the vertices--an approximately linear relation has been found between the light spot position along an axis and the log ratio of the corresponding output currents. The transient responses of these configurations are discussed, and the utility of operation in the small-signal mode is illustrated with some typical parameter values.