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Modelling of base transit time in Si/Si1-y-z Ge yCz/Si HBTs and composition profile design issue for its minimization
Published in -
Volume: 18
Issue: 11
Pages: 907 - 913
From a practical point of view, incorporation of a small amount of C in the base of Si/SiGe/Si HBT eliminates the problems of B outdiffusion and of lattice mismatch. We have developed in this paper a generalized model for the calculation of base transit time τb, for such HBTs. In our model, we have considered the effect of emitter-base and collector-base depletion widths and the variation of saturation-drift velocity in the base-collector depletion region with molar Ge content. It is observed that τb becomes smallest for triangular material (Ge and C) profiles as compared to box type and trapezoidal profiles. In addition the triangular Ge profile with C codoping does not affect film stability and device performance. Our calculation shows that for the same value of strain between Si and SiGe and between Si and SiGeC, the latter device yields the smaller value of τb.
About the journal
JournalSemiconductor Science and Technology
Open AccessNo