823-mA/mm Drain Current Density and 945-MW/cm2 Baliga’s Figure-of-Merit Enhancement-Mode GaN MISFETs With a Novel PEALD-AlN/LPCVD-Si3N4 Dual-Gate Dielectric

Abstract

In this letter, we demonstrate a novel PEALD-AlN/LPCVD-Si3N4 dual-gate dielectric employed in enhancement-mode GaN MISFETs, where the gate recess is fabricated based on our proposed self-terminating gate recess etching technique using a GaN cap layer as recess mask. By using LPCVD-Si3N4 and PEALD-AlN dual-gate dielectric layer, the devices exhibit a high-quality gate dielectric and a good GaN channel interface, yielding a high gate swing up to 18 V and a high channel effective mobility of 137 cm $^{\textsf {2}}/\textsf {V}\cdot \textsf {s}$ at such high gate bias. Thus, the fabricated devices feature a high maximum drain current density of 823mA/mm, a threshold voltage of 2.6 V, an on-resistance of $7.4~\Omega \cdot \textsf {mm}$ , and an ON/ OFF current ratio of 108 with gate–drain distance of $2~\mu \text{m}$ . Meanwhile, a high off-state breakdown voltage of 1290 V is achieved with 10- $\mu \text{m}$ gate–drain distance. The corresponding specific on-resistance is as low as 1.76 $\text{m}\Omega \cdot \textsf {cm}^{\textsf {2}}$ , leading to a high Baliga’s figure of merit of 945 MW/cm2.