We report photoreflectance studies on GaAs/(Al,Ga)As multiple quantum wells grown on Si and Ge substrates. The sharp spectral features observed from various subband transitions indicate that good epilayer quality can be obtained on nonpolar substrates using suitable growth techniques. The experimental results agree well with calculated values based on the envelope function approximation, when the effect of residual strain resulting from the large difference in thermal expansion between GaAs and Si is taken into account.

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