Lateral AlxGa1−xN power rectifiers with 9.7 kV reverse breakdown voltage

${\mathrm{Al}}_x{\mathrm{Ga}}_{\text{1−x}}\mathrm{N}$ $\text{(x=0–0.25)}$ Schottky rectifiers were fabricated in a lateral geometry employing $p^{+}$ -implanted guard rings and rectifying contact overlap onto an ${\mathrm{SiO}}_{\mathrm{2}}$ passivation layer. The reverse breakdown voltage ${\mathrm{(V}}_B)$ increased with the spacing between Schottky and ohmic metal contacts, reaching 9700 V for ${\mathrm{Al}}_{\mathrm{0.25}}{\mathrm{Ga}}_{\mathrm{0.75}}\mathrm{N}$ and 6350 V for GaN, respectively, for 100 μm gap spacing. Assuming lateral depletion, these values correspond to breakdown field strengths of ${\text{⩽9.67×10}}^5 {\mathrm{V cm}}^{\mathrm{-1}},$ which is roughly a factor of 20 lower than the theoretical maximum in bulk GaN. The figure of merit ${\mathrm{(V}}_B{)}^2{\mathrm{/R}}_{\mathrm{ON}},$ where $R_{\mathrm{ON}}$ is the on-state resistance, was in the range 94–268 MW cm⁻² for all the devices.