The low-frequency characteristics of lattice-matched (x = 0.53) and strained (0.60 ≤ x ≤ 0.70) InxGa1-xAs/InAlas HEMTs (high-electron-mobility transistors) are studied. Low-frequency noise measurements reveal shallow traps of 0.078 eV to 0.18 eV which have a slight dependence on In composition. The input noise spectra are almost insensitive to In percentage, but the output spectra suggest that the noise increases with strain. This is related to the increase of device gain with In composition and indicates that a compromise has to be made between high gain (large excess In%) and low noise (low excess In%). Transconductance dispersion is observed only under large gate bias and is absent when the device is biased for maximum gm. Trap densities seem to be largest for lattice-matched devices and minimum for 60% In channels.
