We have observed a significant persistent photoconductivityeffect in narrow InGaAs/InP quantum wellsgrown by metalorganic vapor phase epitaxy. This effect enables a detailed study of transport parameters as a function of the electron density. In this way, the interface roughnessscattering can be separated from the strongly density dependent Coulomb scattering. For different preparation conditions, we find a strong correlation between the amount of interface roughnessscattering and structural data of the interface. The ratio of quantum to classical scattering times remains ≪1 even in the case when Coulomb scattering is not the predominant scattering mechanism.