Integrated filter-less BiCMOS sensor for RGB-LED color determination

In this work an integrated filter-less BiCMOS based color sensor is presented. It is capable of determining the center wavelength of a monochromatic light source in the visible range. This can be used e.g. to determine the three different light colors of an RGB-LED. The detector is based on the effect that the penetration depth in silicon depends on the wavelength of the incident light. It is built up of three vertically stacked pn junctions - a shallow pn junction as blue light detector, a middle pn junction for sensing the green part of incident light and a deep diode to detect red light. The resulting RGB output is used to discriminate between the three different light colors of an RGB-LED. The sensor was characterized with a sweep able monochromatic light source. The sensor is fabricated in a standard 0.6 μm BiCMOS process without using any additional filter layers. This makes it possible to integrate the sensor with other circuitry into a single chip without process modifications.