Activation energy of frequency-dependent drain-conductance of AlGaN/GaN HEMT evaluated with low frequency S-parameters

In this paper, we reveal an activation energy of a frequency-dependent drain conductance in AlGaN/GaN HEMT. Firstly, using two-port vector network characteristics at a low frequency less than MHz, it is confirmed that frequency dependence of a drain conductance (Gd) results in peculiar behavior in S22 of the AlGaN/GaN HEMT. In order to obtain the activation energy of the process of the frequency response of the Gd, we evaluate temperature dependence of a time constant (τ) of the frequency-dependent Gd, which can be obtained by exponential fitting of the Gd. With an Arrhenius plot for the Gd, the activation energy of the process can be estimated to be 0.13 eV. This activation energy is as exactly same as that we obtained from pulsed I-V measurements with which an electron capture process can be evaluated. Therefore, peculiar behavior in S22 we observed in very low frequency two-port network measurements is concluded to result from the electron capture process in the epitaxial layer.