In this study, a gallium nitride (GaN) substrate and its 15 μm epitaxial layer were entirely grown by adopting the hydride vapor phase epitaxy (HVPE) technique. To enhance the breakdown voltage (V_BR) of vertical GaN-on-GaN Schottky barrier diodes (SBDs), a dual ion coimplantation of carbon and helium was employed to create the edge termination. The resulting devices exhibited a low turn-on voltage of 0.55 V, a high I_on/I_off ratio of approximately 10⁹, and a low specific on-resistance of 1.93 mΩ cm². When the ion implantation edge was terminated, the maximum V_BR of the devices reached 1575 V, with an average improvement of 126%. These devices demonstrated a high figure of merit (FOM) of 1.28 GW cm^–2 and showed excellent reliability during pulse stress testing.