In this paper, we report record DC and RF performance in β-Ga₂O₃ High Electron Mobility Transistor (HEMT) with field-plate T-gate using 2-D simulations. The T gate with head-length L_HL of 180 nm and foot-length L_FL of 120 nm is used in the highly scaled device with an aspect ratio (L_G/t_barrier) of ~ 5. The proposed device takes advantage of a highly polarized Aluminum Nitride (AlN) barrier layer to achieve high Two-Dimensional Electron Gas (2DEG) density in the order of 2.3 × 10¹³ cm^-2, due to spontaneous as well as piezoelectric polarization components. In the depletion mode operation, maximum drain current I_D,MAX of 1.32 A/mm, and relatively flat transconductance characteristics with a maximum value of 0.32 S/mm are measured. The device with source-drain distance L_SD of 1.9 µm exhibits record low specific-on resistance R_ON,sp of 0.136 mΩ-cm^–2, and off-state breakdown voltage of 403 V, which correspond to the record power figure-of-merit (PFoM) of ~ 1194 MW/cm². Additionally, current gain cut-off frequency f_T and maximum oscillation frequency f_MAX of 48 and 142 GHz are estimated. The obtained results show the potential of Ga₂O₃ HEMT for futuristic power devices.