Wavelength detection with integrated filter-less BiCMOS RGB sensor

A filter-less BiCMOS RGB colour sensor for wavelength detection in the wavelength range from 400 to 900 nm is presented. The sensor is based on the effect that light with longer wavelength penetrates silicon deeper than light with shorter wavelength. The detector is formed by three vertically stacked photodiodes: a deep diode used as the sensing element for red light, a middle diode to detect green light and a shallow diode as the blue light detector. The resulting RGB output is used to accurately determine the wavelength of the incident light. The sensor is fabricated in standard 0.6 μm BiCMOS technology without any process modifications.