Use of multichannel heterostructures to improve the access resistance and f/sub T/ linearity in GaN-based HEMTs

The typical access resistance of GaN-based transistors is almost an order of magnitude higher than in other semiconductor materials like Si or GaAs. This very high access resistance represents a major difficulty for the fabrication of high-speed devices where parasitic delays currently dominate. In this paper, the use of high conductivity modulation doped multiple channel heterostructures in AlGaN/GaN HEMTs is demonstrated. This has allowed the engineering of the differential resistance of the access regions in these transistors, allowing a significant improvement of their DC and RF characteristics. In the future, the combination of multiple channels separated by different barrier heights will increase even more the linearity of the AlGaN/GaN HEMTs.