Dual-gate In0.5Ga0.5P/In0.2Ga0.8As pseudomorphic high electron mobility transistors with high linearity and variable gate-voltage swing

In0.5Ga0.5P/In0.2Ga0.8As pseudomorphic high electron mobility transistors (PHEMTs) fabricated using single- and dual-gate methodologies have been characterized with special emphasis on precisely controlling the device linearity and the gate-voltage swing. A composite channel employing a GaAs delta-doped (δ(n+)) sheet and an undoped In0.2Ga0.8As layer characterizes the key features of the proposed PHEMT profile. Better carrier confinement for both the electron and the hole due to the InGaP/InGaAs hetero-interface and superior carrier transport properties at the channel/buffer interface, together with the redistributed carrier profile, contribute to high-linearity performances. On the other hand, high etching selectivity between the GaAs cap and the InGaP Schottky layers makes it possible to precisely position both of the gates. The gate-voltage dependence of transconductance for the first equivalent gate with several VGS2 shows that the available gate-voltage swing is in the range 0-4.0 V.