MAGNETOPHONONS IN SHORT-PERIOD SUPERLATTICES

We report the observation of magnetophonon resonances on the backgroun d of the longitudinal magneto-conductance in short-period GaAs/AlAs se miconductor superlattices. Both the GaAs and the AlAs longitudinal opt ical phonons are observed. We show how the enhancement of the magnetop honon effect with electric field is connected to the shift of the elec tron distribution towards the high-velocity and low-density-of-states region at the midpoint of the reduced Brillouin zone. The observed tem perature dependence can be explained by considering the competition be tween the phonon population and the electron lifetime. The two superpo sed series of the GaAs and the AlAs optical phonons are shifted when h ydrostatic pressure is applied and the relative strength of each serie s changes as the Gamma miniband comes closer to the X states.