Heterojunction bipolar transistor having particular Ge distribut

Details Heterojunction bipolar transistor having particular Ge distribut Heterojunction bipolar transistor having particular Ge distribut

1994-11-28

1995-08-08

Limanek, Robert P.

Active solid-state devices (e.g., transistors, solid-state diode

Heterojunction device

Bipolar transistor

257198, 257378, 257616, H01L 2973, H01L 27082, H01L 2700

Patent

active

054401526

ABSTRACT:
A semiconductor device with HBT that enables the cutoff frequency of the HBT to be restrained from lowering at higher collector current levels. The HBT has an emitter region, a SiGe base region, and first and second SiGe collector regions. The first collector region is adjacent to the base region. The base region has a first distribution of Ge concentration graded as a function of depth. The Ge concentration of the first distribution increases at a first gradient as a function of depth from a base-emitter junction to a base-collector junction. The first and second collector regions have second and third distributions of Ge concentration graded as a function of depth. A minimum Ge concentration of the second distribution is not lower than a maximum Ge concentration of the third distribution. In the vicinity of an interface of the first and second collector regions, Ge concentration of the second distribution decreases at a second gradient as a function of depth to the interface, Ge concentration of the third distribution decreases at a third gradient smaller than the second gradient as a function of depth from the interface toward an opposite end of the interface.

REFERENCES:
G. L. Patton et al., "SiGe-Base Heterojunction Bipolar Transistors: Physics and Design Issues", IEDM Technical Digest, 1990, pp. 13-16.
E. J. Prinz, et al., "The Effect of Base-Emitter Spacers and Strain-Dependent Densities of States in Si/Si.sub.1-x Ge.sub.x /Si Heterojunction Bipolar Transistors", IEDM Technical Digest, 1989, pp. 639-642.

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