Intersubband scattering as a tool to study the symmetry properties of a parabolic quantum well

The electron mobility in parabolic quantum wells is measured as a function of carrier density at low temperatures. The curves display pronounced maxima that indicate the onset of intersubband scattering, i.e. the population of another subband. We find that the population of a given subband only depends on the total carrier density almost independent of the position of the wavefuntion within the well which can be tuned via a front and back gate electrode. This is in agreement with predictions for a perfect parabolic potential. If a potential spike is inserted in the center of the PQW we find a complicated behavior for the mobility versus carrier density maxima which reflects the changed symmetry of the potential.