We formulate on the basis of field‐dependent subband structures a design principle for the TE‐polarized electroabsorption (EA) effect in quantum wells (QWs) that includes all the possible subband‐to‐subband and excitonic absorptions. In contrast with trade‐off between band‐gap‐wavelength shift and exciton oscillator strength in enlarged well widths, the transition from the second valence subband dominantly contributes to the EA enhancement. The reason is clarified in conjunction with the nonparabolicity in the valence‐subband structures. The enhancement of the EA change through the second‐subband transition in lattice‐matched wide QWs can be exploited to build highly efficient EA modulators. ©1995 American Institute of Physics.