The Effect of Various Profiles on the Noise Performance of SiGe HBTs
|Devanshu1, Dr. R.K. Chauhan2
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A fundamental limitation of Silicon bipolar transistors is the inherent tradeoff between the dc current gain and the base resistance. One can overcome this limitation of Si bipolar transistors by introducing Germanium into the base material. In last several decades, silicon-germanium (SiGe) technology has come into the global electronics marketplace for its better noise performance in terms of the minimum noise figure, high speed performance, high cut-off frequency, low base emitter capacitance, low base resistance, high current density. As noise is a component in the transistors that degrades the performance of mobile wireless receivers, amplifiers and oscillators from meeting the essential requirements imposed on them while working at high frequencies in the GHz range. Small noise improvement on device level can have a large effect on the overall system performance. In this paper, an accurate noise model of SiGe HBT having 0.18 μm base width is being presented by observing the behaviour of its noise parameters, that is, minimum noise figure (NFmin), base transit time and a variety of analytical equations are being used to analyse and to compare the minimum noise figure NFmin as a function of the Ge concentration for rectangular or box type profile and the triangular profile of SiGe heterojunction bipolar transistor for the better performance. The results of simulated model have been presented based on VISUAL TCAD Simulator tool.