Impurity cyclotron resonance lines of barrier donor electrons in quantum wells

We have investigated by numerical simulation the zero-temperature Line broa dening of the cyclotron resonance transitions of a dilute system of randoml y situated barrier donors, with centers consisting of positive donor ions t ired in the barrier region of a quantum well to which are bound electrons i n the adjacent well. inhomogeneous line shapes due to interdonor Coulomb in teractions are obtained. Discussion is restricted to the case in which magn etic fields are sufficiently high that the elections can be treated semicla ssically (exchange can be neglected). The simulations indicate that a monol ayer of donor ions produces a single highly asymmetric and relatively broad line, with the excitation induced by each absorbed photon being shared amo ng a number of donors. However, if the same donor ions are distributed amon g several monolayers the absorption predicted is a finely spaced comb of we ll-resolved relatively narrow transition Lines, each line deriving from a d ifferent monolayer. In this case the excitation induced by an individual ab sorbed photon is more localized. Parameters chosen for the simulation are r ealistic for GaAs-AlxGa1-xAs quantum wells.