Resonance donor states in quantum wells

The energies and wave functions of the resonance states of shallow donors in quantum wells (QWs) are calculated. The calculations are performed in a model of an isolated impurity center using the example of a GaAs/AlGaAs heterostructure. A formula for the probability of a spontaneous emission of polar optical (LO) phonons is derived. It is shown that, in the vicinity of the resonance-state energies, polar electron-phonon interaction is modified. This modification is produced by a hybridization of confinement subbands. Generally, due to hybridization, an electron interacts with phonons simultaneously in two channels (subbands). The absorption cross section for infrared radiation is calculated, taking into account both homogeneous (in the mid-infrared range) and inhomogeneous broadening (in the far-infrared range). The absorption of radiation whose electric field is normal to the heterointerfaces is related to optical transitions to the states near the resonances. Homogeneous broadening of the absorption lines, as well as the LO-phonon scattering rate, depends on the width of the resonance states (the degree of subband hybridization).