Analysis of DC-RF dispersion in AlGaN/GaN HFETs using pulsed I-V and time-domain waveform measurements

AlGaN/GaN HFETs have been analyzed using pulsed I-V measurements and RF time-domain measurements in an attempt to analyze the phenomenon of DC-RF dispersion and achieve maximum RF performance. The pulsed I-V measurements exhibited the common problem of current slump, as did the RF power performance of the device. The RF time-domain waveforms are used to show that the RF knee-walkout increases with drain bias voltage, thus negating any improved power and efficiency performance that a larger voltage swing would achieve. It was also found that the degree of RF knee-walkout changes depending on the class of operation of the device. Although current slump is evident, it is not permanent, and there is negligible degradation of the device after prolonged RF stimulus.