Characterization techniques for temperature-dependent experimental analysis of microwave transistors

Recent research work has been focused upon the effects of temperature on the dc behavior, the small signal performance, and the noise properties of advanced transistors up to microwave frequencies. Several devices have been investigated by means of different experimental systems down to cryogenic levels (50 K). We here present the most interesting results of such extensive investigation, together with the details of the experimental procedures followed. The on-wafer cooling setup was designed and realized in our laboratory. It exhibited a very good performance characterized by either a tight temperature control or a fast settling time over the 220-320 K temperature range. By this temperature-dependent analysis, interesting features of GaAs- and InGaAs-HEMTs are shown and hereby discussed.