Search

In this letter, a device structure of high-resistivity-cap-layer HEMT (HRCL-HEMT) is developed for normally-off p-GaN gate HEMT toward high breakdown voltage and low current collapse. It demonstrates that the breakdown capability and current collapse of the device were effectively improved due to the introduction of a thick HR-GaN cap layer. The fabricated HRCL-HEMT exhibits a high breakdown voltage of 1020 V at ${I}_{\text {DS}} = 10~\mu \text{A}$ /mm with the substrate grounded. Meanwhile, the dynamic ${R}_{\text {on}}$ is only 2.4 times the static ${R}_{\text {on}}$ after off-state ${V}_{\text {DS}}$ stress of 1000 V with the substrate grounded (the OFF to ON switching time interval is set to $200~\mu \text{s}$ ).

In this letter, we report an in-situ predeposition plasma nitridation process, which is adopted to remove the GaN surface oxygen-related bonds and reduce surface dangling bonds by forming Ga-N bonds prior to the low-pressure chemical vapor deposition (LPCVD)Si 3 N 4 deposition. It demonstrates that the Vth hysteresis and current collapse of the device were dramatically improved due to high-quality LPCVD-Si 3 N 4 /GaN interface. The MIS-HEMTs using this in-situ pre-deposition plasma nitridation exhibit a very-low Vth hysteresis of 186 mV at VG-sweep = (-30 V, +24 V), a high breakdown voltage of 881 V with the substrate grounded. Meanwhile, the MIS-HEMT dynamic RON is only 18% larger than the static RON after OFF-state VDS stress of 600 V (the OFF to ON switching time interval is set to 200 μs).

In this letter, a double-gate AlGaN/GaN high electron mobility transistor operated in a synchronized switching mode is demonstrated, and improved dynamic performances are obtained. The additional gate sits on top of the conventional gate and stretches 2/4 μm to the source/drain electrodes, respectively. A positive voltage pulse is applied to the top gate and is synchronized with the ON-OFF switching pulse applied to the conventional gate. Such a double-gate driving method significantly improves the dynamic performances of the device. Moreover, it allows us to investigate the dynamic on-resistance in the drift region in detail.

A novel double-gate AlGaN/GaN HEMT, in which an additional top-gate covers the adjacent regions of a normal gate, was proposed and fabricated for the first time to compare the dynamic characteristics of AlGaN/GaN HEMTs with a source field plate (SFP) and a gate field plate (GFP). During the dynamic characterization, the device was configured in two operation modes: One is the SFP mode with the top gate biased at 0 V, and the other is the GFP mode applying the gate pulse signal on the top gate at the same time. Compared with an AlGaN/GaN HEMT without field plates, both GFP and SFP much improve the dynamic performances. Compared with the SFP, the GFP shows better dynamic performances with a ~ 34% reduction of switch-on delay time and ~ 6% reduction of dynamic on-state resistance. Studying the dynamic characteristics and applying negative voltage on the top gate during the off state, the mechanism differences between the GFP and the SFP are discussed in detail.