Electron-quantum transport in pseudomorphic and metamorphic In$_{0.2}$Ga$_{0.8}$As-based quantum wells

Metamorphic high-electron-mobility transistor (HEMT) structures based on deep In$_{0.2}$Ga$_{0.8}$As quantum wells (0.7 eV for $\Gamma$ electrons) with different metamorphic buffer designs are implemented and investigated for the first time. The electronic properties of metamorphic and pseudomorphic HEMT structures with the same doping are compared. It is found that, over a temperature range of 4–300 K, both the electron mobility and concentration in the HEMT structure with a linear metamorphic buffer are higher than those in the pseudomorphic HEMT structure due to an increase in the depth of the quantum well. Low-temperature magnetotransport measurements demonstrate that the quantum momentum-relaxation time decreases considerably in metamorphic HEMT structures because of enhanced small-angle scattering resulting from structural defects and inhomogeneities, while the dominant scattering mechanism in structures of both types is still due to remote ionized impurities.