We investigate the electronic structure of In1-xGaxAs/GaAs strained quantum wells and the effects of S-doping on the density of states, effective mass, and transition energies via an exact treatment of the Pikus-Bir Hamiltonian. As the carrier density of the delta-doped layer increases, both the conduction and valence subbands exhibit decreasing behaviour, while the density of states and the effective masses are little affected by delta-doping. In this case, since the valence subbands decrease more rapidly with doping concentration, the energies of the transitions from the first valence subband to the conduction states are found to increase.