The far-infrared photoconductivity technique is applied to study the energy spectrum of shallow indium donors in CdTe layers grown by molecular-beam epitaxy. Accurate experimental data are obtained throughout the energy range relevant to study the resonant polaron effect, including the reststrahlen band. A detailed comparaison of the measured 1s→2${\mathit{p}}^{+}$ transition energies is made with the predictions of a variational calculation, in which the electron-phonon interaction is treated as a second-order perturbation. An overall good agreement is found between experiment and theory with the material parameters found in the literature. This gives a Fröhlich coupling constant α=0.286. © 1996 The American Physical Society.

• Received 5 February 1996

DOI:https://doi.org/10.1103/PhysRevB.54.1467