High-bandgap(eg) structure in planar floating-base bipolar phototransistor (pt)

Abstract

A semiconductor bipolar phototransistor (PT) comprises a floating base consisting of a base (b) electrically coupled only to (i) an emitter (e) via an emitter junction (ej); and (ii) a collector (c) via a collector junction (cj) conductively, capacitively or inductively. A substantially planar semiconductor interface is formed between the semiconductor and a dielectric. A semiconductor volume of highest bandgap (Eg) whose bandgap is higher than the bandgap of the remaining semiconductor volume of the semiconductor bipolar phototransistor (PT) within about 1 micron linear distance from the substantially planar semiconductor interface with the dielectric. The emitter junction (ej) comprises an emitter junction (ej) portion with a bandgap lower than the bandgap of the highest bandgap volume. The base (b) comprises a base (b) portion with a bandgap lower than the bandgap of the highest bandgap volume. The collector junction (cj) comprises a collector junction (cj) portion with a bandgap lower than the bandgap of the highest bandgap volume. A first low-doped region of the highest bandgap volume resides within the emitter junction (ej). A second low-doped region of the highest bandgap volume resides within the base (b). A third low-doped region of the highest bandgap volume resides within the collector junction (cj). A minimum linear dimension of the highest bandgap volume is at least 10 nanometers. The highest bandgap volume is substantially single crystalline. The first, second, and third low-doped regions of the highest bandgap volume are not doped to higher than 10/cm.