High quality electron system with variable electron layer thickness in a parabolic quantum well

We report the realization of a high quality electron system with variable areal density (n_s) in a selectively doped, parabolic A_x Ga_1-x As well. For each n_s, quantum oscillations in the magnetoresistance are analyzed to obtain the electron densities of the electric subbands. These densities are in good agreement with the predictions of self-consistent calculations of the subband structure. The data reveal that with increasing n_s, the width of the electron system increases so that the effective three-dimensional density and the Fermi energy remain essentially constant. The dependence of the low-temperature electron mobility on n _s is also reported.