Magnetophonon resonance under hydrostatic pressure in GaAs- AlGaAs and GaInAs-AlInAs heterojunctions.

We report magnetophonon resonance measurements under hydrostatic pressure in GaAs-AlGaAs and GaInAs-AlInAs heterojunctions. The effective mass and the amplitude of the oscillations are measured in the range 150-300K under pressures up to 16 kbar. The observed enhancement of the effective mass above its band- edge value has a relative amplitude of the order of 10% and 30% in the GaAs- and GaInAs- based heterojunctions respectively. Non-parabolicity effects are not sufficient to explain all the details of the measured mass behavior, and the possible influence of magnetic field-dependent screening of the electron- phonon interaction (bringing changes in the polaron correction of the effective mass and on the amplitude of the magnetophonon oscillations) is discussed.