[en] The nonlinearity of multisubband electron mobility µ in a GaAs/Al_xGa_1−xAs wide quantum well structure is studied by varying the well width w and doping concentration Nd_b (Nd_t) lying in the bottom (top) barrier. The electrons diffuse into the well and accumulate near the interfaces forming two sheets of coupled two dimensional electron gases equivalent to a double quantum well structure. It is shown that interchange of doping concentrations Nd_b and Nd_t lead to the enhancement of µ as a function of w as long as N_dt  >  N_db, even though the surface electron density remains unaltered. Further, keeping N_db unchanged, variation of N_dt leads to nonlinearity in µ near the resonance of subband states at N_dt = N_db at which the subband energy levels exhibit anticrossing. The variation of µ becomes prominent by increasing the well width and resonant doping concentration. The nonlinearity in µ is mostly because of the change in the interface roughness scattering potential through intersubband effects due to the substantial changes in the distributions of the subband wave functions around resonance. The results of nonmonotonic variation of µ can be utilized for low temperature coupled quantum well devices