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AssigneeInternational Business Machines Corporation
InventorsEmmanuel F. Crabbe, David L. Harame, Bernard S. Meyerson, Gary Patton, Johannes M. C. Stork
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A heterojunction bipolar transistor having a single-crystal emitter with reduced charge storage and acceptable current gain is described herein. The heterojunction transistor comprises a collector region, a base region formed on the collector region, and a single-crystal emitter region grown on the base region by low temperature epitaxy. During the formation of the base region, a graded profile of 5-23% germanium is added to the base, as the distance to the collector region decreases, thereby decreasing the base bandgap as it approaches the collector region. Further, during the formation of the emitter region, a graded profile of 0-20% germanium is added to the emitter as the distance from the emitter-base junction increases. Thus, the emitter bandgap decreases as it moves farther from the emitter-base junction. The result of the above grading profiles is that the emitter bandgap is narrower at the emitter contact than the base bandgap at the emitter-base junction.
A heterojunction transistor comprising:
A heterojunction bipolar transistor comprising:
In a method of fabricating a bipolar transistor having a single-crystal emitter region including an emitter contact, a base region, and a collector region, the improvement comprising:
A heterojunction transistor, comprising:
In a method of fabricating a bipolar transistor having a single-crystal emitter region including an emitter contact, a base region, and a collector region, the improvement comprising the step of grading a bandgap in said emitter region such that said bandgap decreases as the distance to said emitter contact decreases, whereby charge storage in said emitter region is reduced, said bandgap being narrower at all points within said emitter region than at a junction between said base and emitter regions, and said emitter and base regions having a bandgap discontinuity substantially proximate to said junction of between about 0 to 0.04 eV.
Dependencies are inferred from the claim text.