Fabrication of sub-50-nm-gate i-AlGaN/GaN HEMTs on sapphire

Abstract

We fabricated sub-50-nm-gate i-AlGaN/GaN high electron mobility transistors (HEMTs) on sapphire and measured their DC and RF characteristics at room temperature. The fabricated HEMTs exhibited true device operation and good pinch-off characteristics down to a gate length Lg of 25 nm. For the HEMTs with a source-drain spacing Lsd of 2 μm, we obtained the Lg dependence of the cutoff frequency fT under a drain-source voltage Vds of 3 V. The peak fT was measured to be 102 GHz at Lg = 35 nm. At Lg = 25 nm, fT started to decrease due to the short-channel effect. The highest fT of 110 GHz was obtained by reducing Lsd from 2 to 1.5 μm and by increasing Vds from 3 to 4 V. © 2003 WILEY-VCH Verlag GmbH & Co. KGaA.