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A normally- OFF AlGaN/GaN high-electron-mobility transistor (HEMT) with p-GaN gate was fabricated on free-standing GaN substrate. The self-terminated etching technology was achieved by combining with AlN stop layer and SF6-based etching gas. Compared with HEMT on Si substrate (Si-HEMT), the HEMT on GaN substrate (GaN-HEMT) demonstrated the higher current density, lower subthreshold swing (SS), lower drain leakage current, and lower static and dynamic ON-resistance that were ascribed to the lower dislocation and less defect on free-standing GaN substrate. Meanwhile, the excellent ${V}_{\mathrm{th}}$ stability up to 175 °C and uniformity was demonstrated. Also, higher breakdown voltage (BV) of 683 V was measured, which was higher than 507 V for Si-HEMT. Hence, a normally- OFF AlGaN/GaN HEMT on free-standing GaN substrate shows good potential in power application. [ABSTRACT FROM AUTHOR]

In this work, the dual junction-high-electron-mobility-transistor (DJ-HEMT) was investigated. The thin AlGaN was grown between the p-GaN gate and gate metal. In the TCAD simulations, the band gap and electric field were shown in this letter, proving the dual junction forming. Moreover, DJ-HEMT shows the high gate voltage swing due to the dual junction at the gate region of device, which enhance gate performance. By contrast with standard p-GaN HEMT (ST-HEMT), DJ-HEMT shows higher $\text{V}_{\text {TH}}$ of 2V, saturation current of 187mA/mm, $\text{I}_{\text {ON}}/\text{I}_{\text {OFF}}$ ratio of $5.1\times 10^{{8}}$ and gate swing voltage which is higher than 20V. In addition, DJ-HEMT also shows the lower device leakage current and superior life time measurement due to the thicker and higher barrier of AlGaN cap layer. [ABSTRACT FROM AUTHOR]