PHOTODIODES WITH PN-JUNCTION ON BOTH FRONT AND BACK SIDES

摘要

The present invention is directed toward a dual junction photodiode semiconductor device. The photodiode has a semiconductor substrate of a first conductivity type, a first impurity region of a second conductivity type shallowly diffused on the front side of the semiconductor substrate, a second impurity region of the second conductivity type shallowly diffused on the back side of the semiconductor substrate, a first PN junction formed between the first impurity region and the semiconductor substrate, and a second PN junction formed between the second impurity region and the semiconductor substrate. Since light beams of a shorter wavelength are absorbed near the surface of a semiconductor, while light beams of a longer wavelength reach deeper sections, the two PN junctions at front and back sides of the photodiode allow the device to be used as an adjustable low pass or high pass wavelength filter detector.