INTERSUBBAND SCATTERING AS A TOOL TO STUDY THE SYMMETRY PROPERTIES OFA PARABOLIC QUANTUM-WELL

The electron mobility in parabolic quantum wells is measured as a func tion of carrier density at low temperatures. The curves display pronou nced maxima that indicate the onset of intersubband scattering, i.e. t he population of another subband. We find that the population of a giv en subband only depends on the total carrier density almost independen t of the position of the wavefuntion within the well which can be tune d via a front and back gate electrode. This is in agreement with predi ctions for a perfect parabolic potential. If a potential spike is inse rted in the center of the PQW we find a complicated behavior for the m obility Versus carrier density maxima which reflects the changed symme try of the potential.