SYSTEM FOR DIRECT MEASUREMENT OF THE STEP RESPONSE OF ELECTRONIC DEVICES ON THE PICOSECOND TIME-SCALE

We have built a system capable of measuring the step response of III-V electronic devices on the picosecond time scale, with no alteration i n device design or epitaxy. To switch on the device under test (DUT), we have designed and fabricated a new type of photoconductor, the rece ssed-ohmic photoconductor, which swings 0.45 V with a 2-ps rise time a nd maintains constant output voltage for 100 ps. This switch is monoli thically integrated with the DUT. To measure the output current of the DUT, we have built a Ti:sapphire-laser-based pump-probe direct electr o-optic sampling system that has a minimum detectable voltage of 70 mu V/root Hz and a measurement bandwidth of 750 GHz. The overall system, comprised of the recessed ohmic photoconductor and the electrooptic s ampling system, can be used to measure the step response of III-V elec tronic devices on the picosecond time scale.