Simulations of SiGe HBT's to obtain high ft and fmax

This paper presents simulations of SiGe HBT's to obtain both high cutoff frequency f/sub t/ and maximum frequency of oscillation f/sub max/ devices using Bipole3 device simulation tool. The simulator was first calibrated with physical model parameters that have already been published and widely accepted. The next step was calibration to measurement data. A SiGe HBT with 50 nm base width was then simulated. This HBT doping and Ge profiles was optimized to obtain high f/sub t/ and f/sub max/ devices. The effect of bandgap narrowing due to heavy doping and Ge mole fraction, doping and Ge dependent minority and majority carrier mobilities were included in the simulation. The SiGe layers were keeping below the critical layer thickness of SiGe layer. The effect of device dimensions, doping profiles, and Ge profiles to the collector and base current, cut-off frequency, and maximum oscillation frequency were also study. The optimized SiGe HBT's reach maximum f/sub t/ and f/sub max/ above 80 GHz.