Measurement of multigigahertz waveforms and propagation delays in modulation-doped field-effect transistors using phase-space absorption quenching.

High-speed waveforms (up to 20 GHz) in InGaAs/InAlAs modulation-doped field-effect transistors (FETs) are measured using 10–20 ps optical probe pulses via the quenching of the absorption in the quantum well gate channel due to Pauli exclusion. The technique is a noncontact probe of the charge density in the gate, and hence, of the logic state of the FET. This charge-sensitive probing technique is combined with voltage-sensitive electro-optic sampling to study internal dynamics of the FET. A gate channel charging time of 11 ps and a gate to drain propagation delay of 15 ps are measured. [ABSTRACT FROM AUTHOR]