Downscaling HEMT devices is nowadays substantial to allow their operation in the millimeter wave frequency domain. In this work, the electrical parameters of three different AlN/GaN structures featuring various GaN channel thicknesses were compared. After a DC electrical stabilization procedure, 96 HEMT devices under test exhibit a minor dispersion in DIBL and lag rates, which reflects an undeniable technological mastering and maturity. Evaluation of the sensitivity of devices with different geometries at temperatures of up to 200°C revealed that the gate-drain distance impacts Ron variation and not I dss variation with temperature. We also showed that DIBL at moderate electrical field and the drain lags exhibit athermal behavior; unlike gate lag delays which can be thermally activated and exhibit a linear temperature dependence regardless of the size of the gate length and gate-to-drain distance.