Importance

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Abstract

An integrated circuit includes a photo diode having a first electrically isolated portion of an epitaxial layer of a first conductivity type, a first semiconductor layer of a second conductivity type disposed therein, a second semiconductor layer of the first conductivity type disposed in the first semiconductor layer, and a third semiconductor layer of the second conductivity type disposed in the second semiconductor layer. A vertical bipolar transistor connected to the diode includes a collector layer including a second electrically isolated portion of the epitaxial layer of the first conductivity type, a base layer of the second conductivity type, disposed therein, which base layer is approximately as thick, in a direction X perpendicular to the surface, and is doped with an approximately equal concentration of impurities, as the first semiconductor layer of the photo diode, and an emitter layer of the first conductivity type disposed in the base layer which is approximately as thick, in the direction X, and is doped with an approximately equal concentration of impurities, as the second semiconductor layer of the photo diode. The second semiconductor layer is doped with a concentration Y of impurities and has an active region with a thickness W.sub.1 in the direction X and the base layer is doped with a concentration Z of impurities and has an active region with a thickness W.sub.2 in the direction X such that ##EQU1## where x is measured in the direction X.

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First Claim