Characterization of Parabolic Quantum Wells Using C-V Profiling

We have measured the C-V characteristics of parabolic quantum wells on which a front gate has been evaporated. The wells were formed by appropriately grading a digital alloy of GaAs/Al sub (x) Ga sub (1-x) As. Classically, one would expect the capacitance to decrease continuously as the electrons are removed from the well by the action of the gate bias. In our measurements, we observe that the capacitance decreases in a sequence of broad steps as the electron density is decreased.