High‐frequency InAlN/GaN HFET with f max over 400 GHz

Abstract

Ultra-thin InAlN/GaN heterostructure field-effect transistors (HFETs) having high maximum oscillation frequency (f max) are fabricated by scaling lateral dimensions. A 3 nm GaN cap layer is adopted to reduce the electron density and suppress the short-channel effects. Non-alloyed regrown n+-GaN ohmic contacts with total ohmic resistance (R tot) of 0.13 Ω.mm is also introduced into the device, in which the virtual source-to-drain distance is 600 nm. T-shaped gate with 40 nm length is formed in the centre of the source-to-drain region by self-aligned e-beam lithography. The peak extrinsic transconductance (g m) reaches 956 mS/mm. Most of all, a high f max of 405 GHz is obtained, which is the highest value among the reported InAlN/GaN HFETs. These obtained results mean that the InAlN/GaN HFETs having reliability should be still suitable for G-band (140–220 GHz) power-amplifier application with further optimisation.