Current–voltage and reverse recovery characteristics of bulk GaN p-i-n rectifiers

$\mathrm{p-i-n}$ rectifiers were fabricated on epitaxial layers grown on free-standing GaN substrates. The forward turn-on voltage, $V_F$ was $\text{∼5\hspace{0.17em}}\mathrm{V}$ at 300 K and displayed a positive temperature coefficient. The specific on-state resistance ${\mathrm{(R}}_{\mathrm{ON}})$ was $\text{∼5\hspace{0.17em}}\mathrm{m}\mathrm{\Omega }{\mathrm{cm}}^2$ at 300 K, with an ideality factor of $\text{∼2}$ and activation energy for low forward current density of $\text{∼1.6\hspace{0.17em}}\mathrm{eV}.$ This is consistent with carrier recombination in the space charge region via a midgap deep level. The figure-of-merit, $V_B^2{\mathrm{/R}}_{\mathrm{ON}},$ where $V_B$ is the reverse breakdown voltage, was $\text{0.32\hspace{0.17em}}{\mathrm{MW cm}}^{\text{−2}}.$ The reverse recovery time was $\text{⩽600\hspace{0.17em}}\mathrm{ns}$ at 300 K. The improved forward characteristics relative to previous heteroepitaxial $\mathrm{p-i-n}$ GaN rectifiers show the advantages of employing a GaN substrate to make a true vertical transport geometry device.