International Business Machines Corporation

Uli Klepser

Mark B Ritter

Joachim Norbert Burghartz

An integrated circuit-compatible photo detector is disclosed which is particularly compatible with BiCMOS fabrication processes. In a first aspect, the photo detector is formed as a lateral phototransistor having a semiconductor substrate, a base structure formed as a first impurity region in the substrate, an emitter structure formed as a second impurity region in the first impurity region, and a collector structure formed by the substrate and by a pair of third and fourth impurity regions in the substrate on opposite sides of the first and second impurity regions. An emitter contact is electrically connected to the second impurity region, while a pair of collector contacts are electrically connected to the third and fourth impurity regions and to each other. An anti-reflective coating is applied to at least the base structure. Advantageously, if a photodiode is required instead of a phototransistor, the second impurity region can be formed with the same polarity as the first impurity region, in which case the first and second impurity regions form a cathode (or anode) and the third and fourth impurity regions form an anode (or cathode). In a second aspect, the photo detector is formed as a lateral phototransistor having a semiconductor substrate, a base structure formed by the substrate, an emitter structure formed as a first impurity region in the substrate, and a collector structure formed as a pair of second and third impurity regions in the substrate on opposite sides of the first impurity region. An emitter contact is electrically connected to the first impurity region, while a pair of collector contacts are electrically connected to the second and third impurity regions and to each other. An anti-reflective coating is applied to at least the base structure. Advantageously, if a photodiode is required instead of a phototransistor, the first impurity region can be formed with the same polarity as the substrate, in which case the substrate and the first impurity region form an anode (or cathode) and the second and third impurity regions form a cathode (or anode).

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Munich, Germany

Uli Klepser