Influence of strong magnetic fields on the ionization of the modulation-doped donors in AlxGa1 − xAsGaAsAlyGa1 − yAs single quantum wells

In the presence of a strong magnetic field (B) applied perpendicular to the interface of a two-dimensional electron system (2DES), the density of states for a 2D electron gas differs sharply from that at zero-magnetic field, which results in the total number of electrons in the structure differing from that at B=0 and consequently in the variation of the ionization of the dopants with magnetic field. In this paper, we observe this effect through calculating self-consistently the electronic structure in a 2DES in strong magnetic fields. By considering Si modulation-doped AlxGa1 − xAsGaAsAlyGa1 − yAs single quantum wells, we study the dependence of 2D electron density and depletion length on the applied magnetic field. Our results show that: (1) the sawtooth-shaped total electron density (nT) and depletion length (zd) can be viewed by plotting nT and zd as a function of B; (2) in the quantum Hall plateaus nT and zd increased linearly with magnetic field; (3) in the steepness regimes of the quantum Hall effect the step changes of nT and zd can be observed and the shape of the step changes depends on the shape of the density of states, and (4) the above mentioned (1)–(3) depends very little on the asymmetric modulation doping and on the applied gate voltage.