A Novel Free-Standing Absolute-Voltage Probe with 2.3-Picosecond Resolution and 1-Microvolt Sensitivy

Due to rapid advances made in high-speed electronic and optoelectronic devices, there is increasing need for noninvasive, external probes with picosecond temporal resolution. Further improvements must include absolute-voltage measurement with microvolt sensitivity and submicrometer spatial resolution. Until now e-beam [1] and electrooptic sampling [2] techniques have been the primary tools utilized. E-beam testing is capable of submicrometer spatial resolution with 50-ps temporal resolution, while electro-optic testing is subpicosecond with 5-µm spatial resolution. In this paper we report on an alternative approach based on the technique of photoconductive sampling [3] that holds promise of single-picosecond temporal resolution and single-micrometer spatial resolution. In previous work using photoconductive sampling the "probe" was integrated into the device under study in the form of a photoconductive gate.[4] We now report on a free-standing photoconductive-type probe with 2.3-ps temporal resolution and 1-µV sensitivity.