Novel methods of growing graded gap structures are described. In order to provide a check that the structures are indeed graded in the correct manner, magnetic ions in the structure have been employed. The good agreement between the predicted and observed Zeeman splitting of the corresponding light- and heavy-hole exciton transitions, together with the magnetic field dependence of the Zeeman splittings and intensity of a forbidden heavy-hole exciton transition, is taken as direct evidence that graded gap structures having the correct composition have indeed been fabricated.