Characteristics of InxAl1-xAs/InxGa1-xAs (x=50%, 60%) metamorphic HEMTs on GaAs substrates

We have developed the In_xAl_1-xAs/In_xGa_1-xAs (x = 50%, 60%) metamorphic HEMTs (m-HEMTs) on GaAs substrates. The current gain cut-off frequency (f_T), and the threshold voltage have been investigated versus the gate-length. The improved microwave performance in smaller gate-length devices is mainly associated with the reduction of the electron-transit time. After analyzing the extrinsic total delay time, the effective velocity of electrons can be estimated, and the velocities are 2.3 × 10⁷ and 2.8 × 10⁷ cm/s for the indium composition of 50% and 60% in the InGaAs channel, respectively.