Analysis of CMOS Photodiodes—Part I: Quantum Efficiency

An improved one-dimensional (1-D) analysis of CMOS photodiode has been derived in which the effect of the substrate, which forms a high–low junction with the epitaxial layer, has been included. The analytical solution was verified with numerical simulations based on parameters extracted from a standard 0.35 m CMOS process. Two empirical parameters are suggested to offset the unavoidable inaccuracies in the extracted parameter values. The derived semiempirical expression exhibits a good agreement with the measured spectral response. In Part II of this paper, a three-dimensional (3-D) analysis of lateral photoresponse in CMOS photodiode arrays is presented along with an empirical modeling method utilizing test linear photodiode arrays.