Cryogenic characteristics of sub‐100‐nm‐gate AlGaN/GaN MIS‐HEMTs

We measured DC and RF characteristics at 300 and 16 K of sub‐100‐nm‐gate AlGaN/GaN metal‐insulator‐semiconductor (MIS) high electron mobility transistors (HEMTs) that had SiN/SiO 2 /SiN triple‐layer insulators. The drain‐source current and the maximum transconductance increased as expected. We observed an increase of 14 to 28% in the value of cutoff frequency f T at 16 K over that at 300 K. At 16 K, we obtained a maximum f T of 176 GHz at a gate length L g of 45 nm. We estimated the average electron velocity under the gate by a transit time analysis. The average velocities were 2.2 × 10 7 cm/s at 300 K and 2.7 × 10 7 cm/s at 16 K. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)