Electronic Raman scattering and infrared absorption spectra of shallow acceptors in ZnTe

Electronic Raman scattering and infrared absorption have been measured for shallow acceptors As, P, and Li in ZnTe. The spectra are interpreted in terms of electronic transitions between bound hole states, some of them being phonon assisted. The valence-band parameters of ZnTe have been deduced by fitting the calculation of Baldereschi and Lipari to the experimental results. Estimated values are close to those obtained from cyclotron resonance experiments. Broadening of some electronic transition bands has been observed in both Raman and infrared spectra, which can be attributed to the mixing of the two-phonon state and the electronic excitation. TO- and LO-phonon sidebands of the electronic transition from the $1s$ to $2s$ state have been observed for the three acceptors. The energy of the LO phonon associated with this transition has been found to be smaller than that corresponding to the $\Gamma$ point. The mechanism of this energy lowering is discussed.