The results of magnetotransport measurements are used to investigate the scattering mechanisms and hence to determine the alloy disorder scattering potential in modulation-doped In0.53Ga0.47As/In 0.52Al0.48As heterojunction samples with spacer layer thickness in the range from 0 to 400 Å. The experimental data for the temperature dependence of Hall mobility are compared with the electron mobility calculated for major scattering processes by using the theoretical expressions available in the literature. It is found that alloy disorder scattering and polar optical phonon scattering are the dominant scattering mechanisms at low and high temperatures, respectively. However, the effects of acoustic phonon scattering, remote-ionized impurity scattering, background-ionized impurity scattering, and interface roughness scattering on electron mobility are much smaller than that of alloy disorder scattering, at all temperatures. The alloy disorder scattering potential is determined by fitting the experimental data for low-temperature transport mobility of two-dimensional electrons in the first subband of the heterojunction sample with the calculated total mobility. © 2005 Springer Science + Business-Media, Inc.