<p>Temperature has a major impact on the performance and reliability of high-frequency AlGaN/GaN HEMTs for high-power applications. Despite substantial research, these devices’ multi-bias behavior throughout a wide temperature range is still poorly understood. This study investigates DC, electrostatic, nonlinear, and analog/RF parameters from − 40 to 150&#xa0;℃ to fill this gap. The performance of GaN HEMT was evaluated by examining ON/OFF-state currents, subthreshold features, transconductance (g_m), and its derivative, along with related parameters such as IMD₃, 1-dB CP, and THD, which were evaluated together with RF performance indicators, including gain (A_v) and gate-to-drain capacitance (C_gd). The transconductance generating factor (TGF), together with the product such as gain frequency (GFP), gain bandwidth (GBW), transconductance frequency (TFP), and gain transconductance frequency (GTFP), was also investigated. Among the electrostatic performance parameters, the currents in the ON state decreased, and the OFF state displayed an increasing trend as the temperature increased. The S-slope and S-swing, on the other hand, show a reverse trend with temperature. Both the current and the g_m, along with its derivatives (g_m2 and g_m3), exhibit a declining trend as the temperature increases. The nonlinear performance of VIP₂, VIP₃, IIP₃, 1-dB CP, IMD₃, and THD, which rely on g_m,is decreased with temperature. In terms of RF parameters, the A_v, C_gd, f_t, and f_max, as well as the TGF and GFP, are found to decrease with temperature. Meanwhile, the GBW, TFP, and GTFP all demonstrate an increasing trend with temperature. These findings provide valuable insights into the thermal impact on device parameters, which can be utilized to promote state-of-the-art technologies for the present and forthcoming deployments.</p>