High frequency Si/Si/sub 1-x/Ge/sub x/ heterojunction bipolar transistors

Abstract

Small-geometry, high-performance Si-Si/sub 1-x/Ge/sub x/ heterojunction bipolar transistors have been fabricated using chemical vapor deposition to form the epitaxial device layers and direct-write, electron-beam lithography. The measured value of f/sub T/ is approximately 29 GHz. Base-collector capacitance is one of the dominant limiting parasitic parameters in the mesa structure used to demonstrate high-speed performance. Advanced epitaxial techniques, such as selective deposition of Si/sub 1-x/Ge/sub x/, should reduce this parasitic element significantly, markedly increasing device speed. Selective deposition of Si/sub 1-x/Ge/sub x/ has been demonstrated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>