Picosecond step-function response of in-plane gate transistor

The high-frequency response of an in-plane gate transistor has been analysed by time-domain transmission measurements using a 20 GHz sampling oscilloscope. Application of a step pulse with 20 ps rise time to the gate of the transistor results in a drain-source current with a rise time of approximately 50 ps. Comparison with the estimated carrier transit time through the channel and with the RC time constant of the device reveals the dominant influence of the parasitic capacitance and the channel resistance on the measured response time.