55 nm gate ion‐implanted GaN‐HEMTs on sapphire and Si substrates

Abstract This paper describes DC and RF characteristics of 55nm gate ion implanted GaN high electron mobility transistors (HEMTs) on sapphire and Si substrates. For DC characteristics, there is no difference in the ion implanted GaN HEMTs on a sapphire and a Si substrate, while RF characteristics are greatly influenced to substrates, especially the HEMTs on a Si substrate are influenced easily, because those have large parasitic capacitance between a substrate and a device compared with a sapphire substrate. The cut off frequency (fT) and the maximum oscillation frequency (fmax) of the HEMT on a sapphire substrate with the gate length (LG) of 55 nm were 108 and 146 GHz, respectively, which were higher than those of a Si substrate. By reducing the source‐drain distance (LSD) to 2 µm from 5 µm, the fT was increased up to 108 GHz from 88 GHz for the ion implanted GaN HEMTs on a sapphire substrate with the LG of 55 nm, whereas for a Si substrate, the fT was increased only 8 GHz. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)