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

This paper reports the design and testing of a CMOS BDJ (Buried Double p-n Junction) detector for developing integrated microanalysis systems. The dev ice 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 photo current ratio I-2/I-1 is considered as the detector response. For photometr ic 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 v ersus wavelength is monotonic increasing when wavelengths are larger than 4 30 nm, A statistical method is employed for sensitivity testing, and noise analysis is performed. At low signal levels, a minimum intensity-independen t noise level, mainly due to noise contributions of the coupled amplifiers, sets a detectivity of about 0.7 x 10(12) cm Hz(1/2) W (1). On-chip integra tion of low-noise preamplifiers may further improve sensitivity performance . (C) 2001 Elsevier Science Ltd. All rights reserved.