Semiconductor device and method for fabricating the same

Abstract

The semiconductor device comprises a collector layer 14; a base layer 16 of a carbon-doped GaxIn1-xAsySb1-y layer having one surface connected to the collector layer 14; an emitter layer 18 connected the other surface of the base layer 16; a base contact layer 30 of a carbon-doped GaAsSb layer electrically connected to the base layer 16; and a base electrode 32 formed on the base contact layer 30. The semiconductor device of such structure can have a much reduced base resistance RB, whereby InP / GaInAsSb-based HBTs including InP / InGaAs-based HBTs can have higher maximum oscillation frequency fmax. Because of the carbon-doped semiconductor layer the semiconductor device can have higher reliability.

Description

[0001] This application is a divisional of application Ser. No. 10 / 092,526, filed Mar. 8, 2002, which is a divisional of application Ser. No. 09 / 191,543, filed Nov. 13, 1998, U.S. Pat. No. 6,399,971.BACKGROUND OF THE INVENTION [0002] The present invention relates to a semiconductor device of a hetero-junction bipolar transistor structure, and a method for fabricating the same. [0003] Recently optical communications systems and mobile communication systems which have high efficiency are required. To make these systems highly efficient semiconductor devices are essential. Hetero-junction bipolar transistors (hereinafter called “HBTs”), which are known as high-speed devices, are one of such devices whose efficiency improvement is prospective. [0004] A structure of a conventional HBT will be explained with reference to FIG. 11. [0005] A collector contact layer 102 formed of an n+-InGaAs layer is formed on a semi-insulating InP substrate 100. A collector layer 104 of an i-InGaAs layer is...

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