Interest in heterostructure field-effect transistors (HFETs) utilizing narrow, heavily doped channels motivates a study of mobility in heavily doped quantum wells. We have measured electron mobility as a function of carrier concentration and temperature in an In0.15Ga0.85As quantum well with a doping of ND=6×1012 cm−2. Mobility is found to rise significantly as the ratio of electron to impurity concentration increases. Even at T=300 K, μ climbs by nearly a factor of 2 as carrier concentration in the well is increased from 1×1012 to 5×1012 cm−2. The results agree qualitatively with recently published theoretical predictions, and suggest that device models utilizing constant mobility are not appropriate for HFETs using doped two-dimensional channels.