(a), and H. LANGE (b) Expressions are derived for the deformation potential constants for pure piezomodulation (PM) and piezoelectrically induced linear electromodulation (LER EM), taking into acoount the difference in sublattice displacements caused by strain and field calculated in a previous paper. It is shown that in case of star degeneracy the sublattice contributions to the deformation potential constants C: and Ci differ in LER EM and PM. The theory is applied to the experimental PM and LER EM spectra a t the El, El -+ dl transitions of GaAs reported in the literature. I n agreement with the predictions of the theory, the deformation potential constant CS, extracted from the LER EM data is found to be much greater than that obtained from PM spectra.
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