Design, Fabrication and Characterization of Γ Gate GaN HEMT for High-Frequency/Wide-Band applications

We report a study on AlGaN/GaN HEMT performances optimization by using Γ-Gate technology. The influence of the adopted technological parameters, like the field plate extension, through the analysis of small/large signal RF performances, including the comparison of the obtained results with conventional LG=0.5µm gate-length devices is investigated. The introduction of a field plate overhang of 0.2µm over the underlying SiN layer at the drain side of the gate foot, has brought approximately to a factor two improvement on the device breakdown voltage. On the other hand, a reduction of RF gain has been observed in presence of the FP metallization, especially if longer than 0.2µm, even though such negative effect is less significant if drain bias higher than 30V has been applied.