Abstract
Precise absolute far–infra-red magneto-transmission experiments have been performed under magnetic fields up to 28 T on a series of single Ga0.24In0.76As quantum wells n-type modulation doped at different levels. The transmission spectra have been simulated with a multilayer dielectric model. This allows us to extract the imaginary part of the optical response function which reveals new singular features related to electron-phonon interactions. In addition to the expected polaronic effects due to the longitudinal (LO) phonons, one observes other interactions with the transverse optical (TO) phonons and a new kind of carrier concentration-dependent interaction with interface phonons. This system provides a unique opportunity to study multiple types of electron-phonon interactions in a single type of compound.