System for direct measurement of the step response of electronic devices on the picosecond time scale

Abstract

We have built a system capable of measuring the step response of III–V electronic devices on the picosecond time scale, with no alteration in device design or epitaxy. To switch on the device under test (DUT), we have designed and fabricated a new type of photoconductor, the recessed-ohmic photoconductor, which swings 0.45 V with a 2-ps rise time and maintains constant output voltage for 100 ps. This switch is monolithically integrated with the DUT. To measure the output current of the DUT, we have built a Ti:sapphire-laser-based pump–probe direct electro-optic sampling system that has a minimum detectable voltage of 70 µV/√Hz and a measurement bandwidth of 750 GHz. The overall system, comprised of the recessed ohmic photoconductor and the electrooptic sampling system, can be used to measure the step response of III–V electronic devices on the picosecond time scale. © 1995, Optical Society of America.