Polaron Zeeman Effect in CdTe

Fourier-transform spectroscopy has been employed to observe the far-infrared absorption resulting from the $1s$ to $2p$ shallow-donor-impurity transitions in CdTe. At zero magnetic field the absorption was found to occur at 87.3 ± 0.3 ${\mathrm{cm}}^{-1\mathrm{}}$. This value compares very well with the prediction of the simple hydrogenic model for shallow-donor-impurity states. The Zeeman splitting of the ($1s\to 2p$) transition was studied in magnetic fields as high as 165 kG. By using the magnetic field to tune energy of the $2p$, $m=+1\mathrm{}$ state first into that of the $1s$ state plus one LO phonon and then into that of the $2p$, $m=-1\mathrm{}$ state plus one LO phonon, it was possible to make the first quantitative determination of the effect of the electron-LO-phonon interaction upon bound electrons. The experimental results were found to be in good agreement with a theoretical calculation for the energy levels of bound polarons. Furthermore, the study of the magnetic field dependence of the ($1s\to 2p$, $m=\pm 1$) transitions has also shown that there are no strong polaron effects due to the electron-TO-phonon interaction in CdTe.