In this paper, we modeled the scattering-limited effective mobility (mu(eff)) of an In0.7Ga0.3As quantum-well (QW) metal-oxidesemiconductor field-effect-transistor (MOSFET). We fabricated In0.7Ga0.3As/In0.52Al0.48As QW MOSFETs with Al2O3 = 2 nm by ALD, and the devices exhibited a mu(eff )value close to 7000 cm(2)/V s at 300 K and good electrostatic integrity. Detailed analysis on mu(eff) of the In0.7Ga0.3As/In0.52Al0.48As QW MOSFETs was performed to investigate various sources of the scattering mechanism, such as surface-roughness scattering (SRS), phonon scattering (PHS) and Coulombic scattering (CS). In doing so, we attempted to separately model the three different scattering mechanisms from their dependency upon the vertical electric field intensity (E-eff). We demonstrated that mu(eff) of the InGaAs QW MOSFET was governed by a combination of three scattering components according to Mathiessen's rule, yielding excellent agreement with experimental data.