Fabrication and characteristics of 0.2-mu m Al0.24Ga0.76As/In0.15Ga0.85As/GaAs pseudomorphic HEMTs with wide-head T-shaped multifinger gates

Abstract

A passivated 0.2-mu m pseudomorphic HERIT (PHEMT) was fabricated by combining a wide-head T-shaped gate formed using the dose split method of electron beam lithography (DSM) and a multifinger-type structure with drain-airbridges for the interconnection of the drain electrodes. The extrinsic transconductance and the cutoff frequency of the PHEMT device were 490 mS/mm and 75 GHz, respectively. The lowest minimum noise figure, NFmin, of the PHEMT device was observed around 40% of the saturation drain current, I-dss, at 12 GHz and a drain-to-source voltage, V-ds, of 2 V. The device exhibited a NFmin as low as 0.38 dB with an associated gain of 10.5 dB at 12 GHz. This noise figure value is the lowest data ever reported for a PHEMT device with the same gate length and multifinger-type gate structure. This result corresponds to a drastic reduction of the gate resistance to 0.2 Omega due to the multifinger-type gate structure with a wide-head T-shaped gate.