Miniband effects in short-period InGaAs

The formation of the miniband electron energy structure and its effect on optical vibrational modes were explored in doped InGaAs/InP superlattices with different periods. The analysis of the high resolution x-ray diffraction and Raman data allowed us to conclude that in spite of the defect structure of the layers constituting the superlattices, their super-periodicity was well defined. The quantitative proof of the conditions for break-down of the Raman selection rules is presented. No Raman selection rules were observed for the longitudinal optical phonons in long-period superlattices. In short-period superlattices the emergence of the selection rules of the coupled plasmon-LO phonon vibrations was demonstrated to occur due to the increase of their coherence lengths.