Noise spectroscopy of AlGaN/GaN HEMT structures with long channels

In this paper we discuss the effect of dissipated power on the characteristic time of noise spectra transformation investigated in wide-bandgap AlGaN/GaN transistor structures with long channels. It is found that the characteristic time as a function of temperature demonstrates an exponential dependence with definite activation energy. Obtained results are explained based on the developed model of non-equilibrium fluctuations of the sample resistance. These fluctuations cause a local overheating due to local change of resistance. In the long channels these fluctuations may create overheating regions with two different self-heating temperatures, leading to different activation dependences, observed in the experiment.