a b s t r a c tWe report the molecular beam epitaxy (MBE) growth and the comparative systematic study of the electrical and thermoelectric characterizations of ScAs:In 0.53 Ga 0.47 As and ErAs:In 0.53 Ga 0.47 As nanocomposites. The peak room-temperature power factor of ScAs:InGaAs is 38% comparing to that of ErAs:InGaAs. The carrier concentration change of the nanocomposites versus the ScAs and ErAs incorporation levels below 2.2% is explained as due to the formation of nanoparticles with different sizes and densities. The carrier concentration difference between the two types of nanocomposites at the same incorporation level of ScAs and ErAs is explained by the size difference between the ScAs and ErAs nanoparticles.