Graded-base Si/Si/sub 1-x/Ge/sub x//Si heterojunction bipolar transistors grown by rapid thermal chemical vapor deposition with near-ideal electrical characteristics

Graded-base and uniform-base Si/Si/sub 1-x/Ge/sub x//Si heterojunction bipolar transistors with near-ideal base and collector currents have been fabricated by rapid thermal chemical vapor deposition. The temperature dependences of the collector currents are shown to obey a simple analytical model of an effective Gummel number. The model can be applied to devices which have arbitrary base profiles. The base currents are independent of base composition, and current gains in excess of 11000 have been observed at 133 K.<
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