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Numerical simulation and analysis of Si$\sb{1-x}$Ge$\sb{x}$ pseudomorphic heterojunction bipolar transistors

Branimir Pejcinovic, University of Massachusetts Amherst


Numerical simulation was used to analyze performance of Si$\sb{1-x}$Ge$\sb{x}$ pseudomorphic heterojunction bipolar transistors (PHBTs). Models for different material properties were developed and used in 2-D drift-diffusion-equations and 1-D hydrodynamic-equations simulation programs. N-p-N and P-n-P PHBTs were analyzed. For N-p-N PHBTs both metal- and poly-Si-emitter contacts were investigated. The figures of merit used are unity current gain frequency f$\sb{T}$ and maximum frequency of oscillation f$\sb{max}$. In all cases analyzed, Si$\sb{1-x}$Ge$\sb{x}$ offers significant advantages over equivalent Si devices: metal emitter N-p-N Si$\sb{1-x}$Ge$\sb{x}$ devices can have f$\sb{T}$ up to two to three times higher than Si; poly-Si emitter N-p-N Si$\sb{1-x}$Ge$\sb{x}$ up to 50% or more higher f$\sb{T}$; P-n-P metal-emitter Si$\sb{1-x}$Ge$\sb{x}$ devices shows similar improvements. f$\sb{max}$ is also improved in all devices, but not as much as f$\sb{T}$. Some devices are actually limited by their f$\sb{max}$ and not f$\sb{T}$ and to improve their performance, f$\sb{max}$ must be increased first by reducing parasitic resistances and capacitances. ^

Subject Area

Electrical engineering|Condensed matter physics

Recommended Citation

Pejcinovic, Branimir, "Numerical simulation and analysis of Si$\sb{1-x}$Ge$\sb{x}$ pseudomorphic heterojunction bipolar transistors" (1990). Doctoral Dissertations Available from Proquest. AAI9110204.