A CMOS Buried Quad p-n Junction Photodetector Model

A buried quad junction (BQJ) photodetector has been designed and fabricated with a high-voltage CMOS process. It implements four vertically stacked p-n junctions with four different spectral responses. This feature allows high spectral discriminating ability, greater than both conventional buried double junction and buried triple junction detectors. In this paper, we propose a SPICE-like model, based on the physical properties of the device structure. The proposed model has been integrated in EDA software. It could be used for rapid and reliable design of system on chip, integrating the BQJ sensor, and its signal processing. The analytical expressions of the four BQJ photocurrents, as well as dark currents, have been developed. The spectral characteristics of the photodetector, computed with the proposed model, have been compared with those from TCAD simulations and experimental measurements. The analytical is close to the measurement with an average error on spectral responses in the range of 3%-17%, depending on the considered junction.