US 5,962,880 A · Heterojunction bipolar transistor

Abstract

A self-aligned bipolar transistor which has a small base resistance and small emitter-base and collector-base capacitances and is operable at high speed is disclosed. This bipolar transistor is characterized in that a low concentration collector region made of single crystal Si--Ge is self-alignedly formed between an intrinsic base of single crystal Si--Ge and an intrinsic base, and that an extrinsic base electrode and an intrinsic base are connected only through a doped external base. With this arrangement, an energy barrier is not established at the collector base interface owing to the formation of the low concentration region of single crystal Si--Ge, so that the transit time of the carriers charged from the emitter is shortened. The connection between the intrinsic base and the extrinsic base electrode via the doped external base results in the reduction of the base resistance. In addition, the self-aligned formation of the emitter-base-collector leads to the reduction in capacitance between the emitter and the base and also between the collector and the base. Accordingly, a high-speed bipolar transistor can be realized and thus, circuits using the transistor are operable at high speed.

Claims18

Dependent claims

A bipolar transistor comprising, at least:

a multilayered film which includes a single crystal silicon layer of a first conductivity type, a first insulating layer formed on the surface of said single crystal silicon layer of the first conductivity type and having an opening therein, a polycrystalline layer of a second conductivity type opposite to the first conductivity type, and a second insulating layer;
a single crystal silicon germanium layer of the first conductivity type formed in the opening;
a single crystal silicon germanium layer of the second conductivity type formed on said single crystal silicon germanium layer of the first conductivity type;
a polysilicon germanium layer formed in contact with both said single crystal silicon germanium layer of the second conductivity type and said polycrystalline layer of the second conductivity type;
and
a second single crystal layer of the second conductivity type which is formed on said single crystal silicon germanium layer of the second conductivity type and is lower in impurity concentration than said single crystal silicon germanium layer of the second conductivity type.

3 more elements

An optical reception system which comprises a photo detector for receiving an optical signal and outputting an electric signal, a first amplifier circuit for receiving the electric signal from said photo detector, a second amplifier circuit for receiving the output from said first amplifier circuit, and a decision circuit for converting the output from said second amplifier circuit into a digital signal in synchronism with a given clock signal,

wherein said first amplifier circuit has a first bipolar transistor including a base connected to said photo detector, and a second bipolar transistor including a base connected to a collector of said first bipolar transistor and further including a collector-emitter path connected to an input of said second amplifier circuit, and wherein at least one of the first and second bipolar transistors comprises:
a multilayered film which includes a single crystal silicon layer of a first conductivity type, a first insulating layer formed on a surface of said single crystal silicon layer of the first conductivity type and having an opening therein, a polycrystalline layer of a second conductivity type opposite to the first conductivity type, and a second insulating layer;
a single crystal silicon germanium layer of the first conductivity type formed in the opening;
a single crystal silicon germanium layer of the second conductivity type formed on said single crystal silicon germanium layer of the first conductivity type;
a polysilicon germanium layer formed in contact with both said single crystal silicon germanium layer of the second conductivity type and said polycrystalline layer of the second conductivity type;
and
a second single crystal layer of the second conductivity type which is formed on said single crystal silicon germanium layer of the second conductivity type and is lower in impurity concentration than said single crystal silicon germanium layer of the second conductivity type.

4 more elements

An optical signal reception system, comprising:

a photo detector for receiving an optical signal and outputting an electric signal;
and
an amplifier circuit having a first bipolar transistor including a base connected to the photo detector for receiving the electric signal, and a second bipolar transistor including a base connected to a collector of the first bipolar transistor and further including a collector emitter path which provides an output of the amplifier,
wherein at least one of the first and second bipolar transistors comprises:
a multilayered film including a single crystal silicon layer of a first conductivity type, a first insulating layer formed on a surface of said single crystal silicon layer of the first conductivity type and having an opening therein, a polycrystalline layer of a second conductivity type opposite to the first conductivity type, and a second insulating layer;
a single crystal silicon germanium layer of the first conductivity type formed in the opening;
a single crystal silicon germanium layer of the second conductivity type formed on the single crystal silicon germanium layer of the first conductivity type;
a polysilicon germanium layer formed in contact with both the single crystal germanium silicon layer of the second conductivity type and the polycrystalline layer of the second conductivity type;
and
a second single crystal layer of the second conductivity type which is formed on said single crystal silicon germanium layer of the second conductivity type and is lower in impurity concentration than said single crystal silicon germanium layer of the second conductivity type.

7 more elements

Dependencies are inferred from the claim text.

Heterojunction bipolar transistor

Life of this patent

Heterojunction bipolar transistor

Life of this patent

Abstract

Claims18