Abstract

We use the phase-space absorption quenching (PAQ) effect as a high-speed optical probe of the carrier density in the channel of an InGaAs/InAlAs modulation-doped FET (MODFET). This effect is caused by the presence of carriers in the quantum well that forms the MODFET channel, which suppresses the optical absorption of the 10 - 20 ps probe pulses at wavelengths near the first subband edge due to Pauli exclusion. Because the technique probes the carrier density in the gate, it can determine the logic state of the MODFET. We combine the charge-sensitive PAQ technique with voltage-sensitive electrooptic sampling to study internal dynamics of the MODFET. A channel charging time of 11 ps and a gate to drain propagation delay of 15 ps are measured.

© 1989 Optical Society of America