The gate voltage dependence of the low-field electron mobility has been investigated in a In0.53Ga0.47As/In0.52Al0.48As modulation-doped heterostructure using a real-time Green's function formalism. All scattering mechanisms relevant for this material system have been incorporated in the theoretical model, including alloy disorder scattering, Coulomb scattering from the ionized impurities in the buffer layer, acoustic phonon, and piezoelectric scattering. The simulation results for the subband structure suggest occupation of two subbands at V-G=0V. Good agreement is observed between the simulated sheet electron densities and the experimentally extracted ones from Hall and Shubnikov-de Haas oscillatory magnetoresistance measurements. The mobility results for the structure investigated suggest that alloy-disorder scattering is the dominant mobility degradation mechanism. (C) 2003 American Vacuum Society.