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US 6,271,098 B1Granted
Heterojunction bipolar transistor and method for producing the same
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsShinichi Miyakuni, Teruyuki Shimura
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Abstract
A heterojunction bipolar transistor is provided with a ballast resistor layer in an emitter layer which prevents the current amplification factor β from decreasing. The n-GaAs carrier supply layer having a specified carrier concentration is formed between the ballast resistor layer and the n-AlGaAs layer.
Claims4
A method for producing a heterojunction bipolar transistor which comprises steps of:
- forming a first conductivity type GaAs collector substrate;
- laminating a second conductivity type GaAs base region, and an emitter region which includes at least a first conductivity type AlGaAs layer, a first conductivity type GaAs carrier supply layer formed on the first conductivity type AlGaAs layer, and a first conductivity type GaAs ballast resistor layer formed on the first conductivity type GaAs carrier supply layer, on the first conductivity type GaAs collector substrate;
- forming a emitter electrode on the emitter region;
- etching the emitter region until the base region is exposed by using the emitter electrode as a mask, thereby forming emitter mesa portions;
- and
- providing a base electrode on the base region and a collector electrode on the collector region, respectively.
3 more elements
Dependencies are inferred from the claim text.