Influence of the calibration kit on the estimation of parasitic effects in HEMT devices at microwave frequencies

In this paper, we investigate how critical the calibration kit is in an accurate estimation of microwave device parasitic elements. The semiempirical cold FET method has been applied to the extraction of the small signal equivalent circuit of several HEMT devices. Two different measurements were made on the same devices by using two calibration kits. The first kit is a commercial one based on the LRM method, whereas the second kit was designed by the authors and fabricated on the same chip of the devices. The discrepancies found in the calculated parasitic elements provided information on the sensitivity of the elements with respect to the calibration kit, and, therefore, on the physical origin of the parasitics. These discrepancies. show that it is possible to evaluate the influence of the contact pads on the electrical behavior of on-chip semiconductor devices by making measurements with different calibration standards.