Electron-Optical-Phonon Interaction in Semiconductor Multiple-Quantum-Well Structures

The $1s-2p(m=+1\mathrm{})\mathrm{}$ hydrogenic transition in magnetic fields up to 20 T for shallow donor impurities confined in 138-Å GaAs wells in AlGaAs/GaAs multiple-quantum-well structures has been used to investigate the electron-optical-phonon interaction. A resonant "pinning" behavior has been observed at energies well below (∼50 ${\mathrm{cm}}^{-1\mathrm{}}$) that of the long-wavelength optical phonons of GaAs. It is suggested that these surprising results may be explained by interaction with near-zone-boundary longitudinal-optical phonons activated by the superlattice.