Improved DC and RF Performance of Novel MIS p-GaN-Gated HEMTs by Gate-All-Around Structure

Abstract

In this study, we report a novel structure of enhancement-mode metal-insulator-semiconductor high electron mobility transistor (E-mode MIS HEMT) with ${p}$ -GaN gate by gate-all-around technology. The gate-all-around structure is fabricated by depositing an insulator and gate to surround the ${p}$ -GaN mesa. The ${p}$ -GaN length is smaller than the gate length, which would easily turn on the two dimensional electron gas (2DEG) of channel and result in a higher drain current and thus improve the device performance. The gate-all-around ${p}$ -GaN MIS HEMT has better gate control, better transconductance, and lower gate leakage current. The device exhibits a threshold voltage ( $\text{V}_{\text {th}}$ ) of 1.5 V, a maximum transconductance ( $\text{G}_{\text {m.max}}$ ) of 101 mS/mm, and a drain saturation current density ( $\text{J}_{\text {DS, max}}$ ) of 412 mA/mm at a gate bias ( $\text{V}_{\text {g}}$ ) of 5 V. The most important achievement is that the gate leakage current at $\text{V}_{\text {g}}= 5$ V is only 10−8 mA/mm. Moreover, the ratio of drain current density to gate leakage current density ( $\text{J}_{\text {DS}}/\text{J}_{\text {GS}}$ ) is 108 at $\text{V}_{\text {g}}= 5$ V. Finally, the cut-off frequency ( $\text{f}_{\text {t}}$ ) and maximum oscillation frequency ( $\text{f}_{\text {max}}$ ) of microwave performance for this gate-all-around device with a $1~\mu \text{m}$ gate length are 6.0 and 9.8 GHz, respectively.