The enhancement of Q factor in RPCVD SiGe varactors by the structural modification of the base-collector junction

Abstract

We designed two silicon germanium (SiGe) varactors enhanced in factor through a structural modification by using a cost-effective SiGe heterostructure bipolar transistor (HBT) process, a conventional reduced-pressure chemical vapor deposition (RPCVD). As a result, the suggested structures showed a superiority in factor (160/GHz/pF at 2.5 GHz) to the conventional one (70/GHz/pF), even with neither a change in process nor an additional mask. We attributed the enhancement of factor to the structural feature of the varactors and quantitatively analyzed it with a lumped element model.

Precise Analysis of Si/Graded-Si1-xGex/Si1-xGex Heterostructure Films Grown by Reduced Pressure Chemical Vapor Deposition Using Spectroscopic Ellipsometry

“…Lots of research works have been devoted to the development of SiGe devices because of not only remarkable improvement in performance but also excellent stability and productivity provided by silicon-based process technology. Several key factors including operation speed, linearity, low frequency noise, and high gain at low current level, could have SiGe heterojunction bipolar transistors(HBTs) to cover state-of-the-art applications such as wireless radio frequency and optical communication chips (1)(2)(3). Recently, the strain-modulated heterostructure substrates and the bandgap engineering extend its application to strained-silicon metal-semiconductor field effect transistors(MOSFETs), infrared photodiodes, and solar cell (4)(5)(6)(7)(8).…”