We report flicker noise measurements combined with deep-level transient spectroscopy of the doped and undoped channel GaN/AlGaN heterostructure field-effect transistors. The low-temperature noise spectra for the doped devices show clear generation-recombination peaks. The value of the activation energy extracted from these noise peaks is consistent with the activation energies measured using deep-level spectroscopy. Our results indicate that the input-referred noise spectral density of the undoped channel devices is much smaller (up to two orders of magnitude) than that of the doped channel devices with comparable electric characteristics. The additional defects due to doping add up to the generation-recombination and flicker noise.
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