This paper discusses the influence of BGaN layer on the structure of Al0.26Ga0.74N/ B0.02Ga0.98N /GaN HEMT with T- Gate. The use of BGaN back barrier on this device enhances confinement of the electron in the device. We simulate DC and AC characteristics by using TCAD Silvaco. The obtained results shows a maximum drain current of 1 A/mm, a threshold voltage of -1.25 V, a maximum transconductance of 0.850 S mm-1, an ION/IOFF ratio of 1.5*109, a Drain Induced Barrier Lowering (DIBL) of 166 mV/V, a Sub-threshold Swing (SS) of 300 mV/dec and a Gateleakage of 5.10-22 A. In terms of AC performances, the device offers Ft of 600 GHz and Fmax of 1 THz. These results revealed that the use of BGaN back barrier has added benefits in performance which can be an outstanding solution for high frequency switching and highpower applications.