Improved linearity, stability, and thermal performance of multi-mesa-channel AlGaN/GaN HEMTs

AlGaN/GaN high-electron-mobility-transistors (HEMTs) are expected to revolutionize the power-switching technology owing to excellent intrinsic material properties of GaN, which include wide bandgap, high carrier saturation velocity, large critical electric field, and good thermal conductivity. However, the widespread deployment of these devices is still hounded by stability issues such as current collapse, kink effect, transconductance collapse, and self-heating. To address these issues, we developed the multi-mesa-channel (MMC) HEMT, in which a periodic trench structure is fabricated only under the gate electrode. The formation of the periodic trench results into parallel nanowire channels with 2-D electron gas (2DEG) surrounded by the gate electrode. A surrounding-field effect in the MMC structure results in a shallower threshold voltage, thus giving another degree of freedom for obtaining enhancement mode operation. In this work, we would present experimental results that demonstrate the superior performance of MMC AlGaN/GaN HEMTs over their conventional planar counterparts. On top of being less vulnerable to current collapse, MMC devices also exhibit improved linearity, stability, and thermal performance, which are all positive attributes required for optimum device operation.