Design and testing of a CMOS BDJ detector for integrated micro-analysis systems

Abstract

This paper reports the design and testing of a CMOS BDJ (Buried Double p–n Junction) detector for developing integrated microanalysis systems. The device is an optical detector producing two photocurrents ( I 1 and I 2) when it receives an incident flux. It can be operated either as a photodetector by using its output current I 1+ I 2, or as a colour detector if the photocurrent ratio I 2/ I 1 is considered as the detector response. For photometric detection, the device has a sensitive response covering the visible and near-IR regions, and for colour detection, the photocurrent ratio I 2/ I 1 versus wavelength is monotonic increasing when wavelengths are larger than 430 nm. A statistical method is employed for sensitivity testing, and noise analysis is performed. At low signal levels, a minimum intensity-independent noise level, mainly due to noise contributions of the coupled amplifiers, sets a detectivity of about 0.7×10 12 cm Hz 1/2 W −1. On-chip integration of low-noise preamplifiers may further improve sensitivity performance.