Pulsed techniques for the characterization of low-frequency dispersive effects in RF power FETs using a flexible measurement set-up

This work describes an on-wafer measurement architecture tailored to the broadband pulsed characterization of radio-frequency (RF) power field-effect transistors (FETs). Based on a 50-Omega environment and corresponding wave-variable domain representation, the set-up exploits the impedance matching and the broadband feature of its components, together with a full-bandwidth calibration, for the synthesis and measurement of pulsed waveforms with short pulse rise/fall times in the order of a few ns, while guaranteeing a reduced risk of oscillations. These measurement capabilities are particularly suited for experimentally assessing the FET performance reduction due to low-frequency dispersive effects caused by thermal and charge trapping phenomena. The flexibility of the set-up is showcased by discussing experimental examples of different measurement techniques in the kHz-to-GHz range, including single-and double-pulsed I-V characteristics and S-parameters, as well as pulsed continuous-wave (CW) measurements, performed on state-of-the-art gallium nitride (GaN) RF FETs for microwave and millimeter-wave applications.