A Δ-shaped gate GaN-based E-mode vertical current-aperture vertical electron transistor (CAVET) device with a borondoped current block layer (B-CBL) on an n + GaN substrate is proposed, designed, and demonstrated herein. Enhancementmode (E-mode) operation is achieved in the proposed device by introducing a 1-μm-thick p-GaN CBL layer into the recessed Δ-shaped gate of the metal-insulator-semiconductor (MIS) high-electron-mobility transistor (HEMT) structure. The device exhibits a threshold voltage of 6.76 V, a drain current saturation of I ds,sat = 3.44 kA/cm 2 , a transconductance of g m = 783.42 S/cm 2 , and an ON/OFF current ratio > 10 10 A/ cm 2 . The breakdown voltage in the OFF-state (V BR,OFF ) shows a maximum of 1590 V and a minimum of 1513 V for a CBL layer thickness (t B-CBL ) of 0.2 and 1 µm at a gate bias of 0 V. The lowest ON-state resistance (R ON ) achieved is 1.24 Ω cm 2 , accompanied by a low gate current of I g,L < 10 -9 and a drain leakage current of I d,L < 10 -8 A/mm. The device exhibits high-frequency performance with peak f t and f max values of 5.12 GHz and 36.8 GHz, respectively, as measured from two-port Y parameters with an Si 3 N 4 thickness (t Si3N4 ) of 40 nm and a recessed penetration depth (t penetration ) of 0.2 µm at V ds = 10 V. Finally, the performance of the vertical CAVET AlGaN/GaN MIS-HEMT power switching device with a boron-doped GaN CBL is analyzed using an ultralow-loss boost converter circuit. The results of the analysis of the demonstrated device indicate that it is a suitable candidate for use in high-power low-loss switching applications.