1/f Noise in As-Processed and Proton-Irradiated AlGaN/GaN HEMTs Due to Carrier Number Fluctuations

We find that the low-frequency 1/f noise of AlGaN/GaN HEMTs before and after 1.8-MeV proton irradiation is more consistent with a carrier-number fluctuation model that includes a non-constant defect-energy distribution D-t(E (f)) than with the Hooge mobility fluctuation model. A strongly varying D-t(E (f)) in these devices is confirmed by measurements of the voltage and temperature dependence of the noise. First-order estimates of effective border-trap density before and after 1.8-MeV proton irradiation are obtained for commercial and research-grade devices using a simple number-fluctuation model. The input-referred noise magnitude of GaN/AlGaN HEMTs decreases at biases that are much more positive than threshold because the gated region of the HEMT comprises a relatively small portion of the channel, and the noise is attenuated by the voltage divider formed by the gated and ungated regions of the channel.