Frequency analysis of the kink effect in AlInAs/GaInAs HEMTs

A frequency analysis of the transconduction and output conduction of 0.25 /spl mu/m InP based HEMTs was carried out using S-parameter measurements down to 1 kHz. The advantage of this method is that very low frequency and hf performance is determined using a single measurement sequence. It has been shown that the kink effect in the output characteristics consists of two ranges of a reduced and an increased drain current. Additionally it was found, that while g/sub d,hf/ increases for more positive gate voltages, g/sub d,dc/ usually decreases. It has also been shown, that the dc measured transconductance g/sub m,dc/ is lower than g/sub m,hf/. This difference is increased for high drain voltages. The frequency analysis shows that g/sub m,dc/ is generally decreased at higher drain voltages. Finally, it has been shown that the dispersion output conduction can be up to the GHz range for high drain source voltages.