IEEE Electron Device Letters

3.9 ps SiGe HBT ECL ring oscillator and transistor design for minimum gate delay

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We show empirical results that demonstrate the effect of high performance SiGe HBT design parameters on the minimum gate delay of an ECL ring oscillator. SiGe HBT devices with a high fMAX (338 GHz) and a low fT (180 GHz) achieve a minimum delay of 3.9 ps, which to our knowledge is the lowest reported delay for a silicon based logic gate. Compared to the extracted (extrapolated) fT and fMAX, a simple figure of merit proportional to √fT/RBCCB with RB and CCB extracted from S-parameter measurement is best correlated to the minimum gate delay.