Design and implementation of integrated BDJ detector in a standard CMOS technology

The integrated BDJ (Buried Double p-n Junction) detector basically consists of two buried junctions for collection of photocarriers at different depths. It can operate non only as a photodetector, but also as a wavelength-sensitive detector, because the ratio of the deep junction photocurrent to the shallow junction photocurrent is wavelength-dependent. The BDJ detector can be implemented using a standard CMOS process. The optimum design for a particular application requires divers considerations, such as process parameters, detector sizing, on-chip interface electronics, temperature sensing and compensation, etc. In particular, some geometrical and electrical parameters have significant effects on the device behavior and performances, and detector size as well as on-chip circuitry should be properly defined to meet specifications. Also, temperature-dependence of characteristics may need to be compensated. Two examples concerning design of integrated BDJ detector for specific applications are shown. One is for detecting spectral changes of absorption, while the other is for building a self-calibrated microspectrophotometer.