Temperature-Dependent Characteristics of GaN Homojunction Rectifiers

Abstract

We report a homojunction gallium nitride (GaN) p-i-n rectifier fabricated on free-standing GaN substrates with the breakdown voltage $>800$ V and low specific on-resistance ( $R_{\mathrm{{\scriptscriptstyle ON}}}A$ ). At 298 K, $R_{\mathrm{{\scriptscriptstyle ON}}}A$ is 0.28 $\text{m}\Omega $ -cm $^{2}$ at the current density ( $J$ ) of 2.5 kA/cm $^{\vphantom {R^{R^{}}}2}$ and the corresponding Baliga’s figure of merit is $>2.5$ GW/cm $^{2}$ . At a given temperature, $R_{\mathrm{{\scriptscriptstyle ON}}}A$ values decrease with $J$ due to conductivity modulation in the drift region. The ambipolar lifetime ( $\tau _{a})$ is also determined by open-circuit voltage decay measurement. The value for $\tau _{a }$ is 9.6 ns at 298 K and it monotonically increases to 22 ns at 448 K. The reverse $I$ – $V$ measurement reveals the reverse leakage current mechanism is mainly attributed to a field-assisted ionization process from deep-level centers in the space-charge region. The analysis of $T$ – $I$ – $V$ curve yields the Poole-Frenkel coefficient ( $\sim 3.1\times 10^{-4} ~\text {eV} \cdot \text {V}^{-1/2}\cdot {\rm cm}^{-1/2})$ and a deep-level trap ( $\sim 0.7$ eV) at zero bias.