Impurity bound polaron in a magnetic field in quantum-well structures

We have proposed a new modified Hamiltonian for a polaron bound to a donor impurity in semiconductor quantum-well structures (QWs) in the presence of an arbitrary magnetic field, in which the coupling of an electron with confined bulk-like LO phonons, half-space LO phonons and interface phonons is considered. In particular, the interaction of the impurity with the various phonon modes is also included in a QW for the first time. We have calculated the ionization energy of a bound polaron in Al-x, Ga1-x, As/GaAs/Al-x, Ga1-x, As asymmetric and symmetric QWs. Results have been obtained as a function of the barrier height (or equivalently of Al concentration x), the well width, the magnetic field intensities and the position coordinates of impurity in the QWs. Our numerical calculations clearly show that the interaction between the impurity and the phonon field plays an important role in screening the Coulomb interaction and consequently changes the binding energy of a bound polaron by a considerable amount. On comparison with the experimental measurements, an excellent agreement is found. (C) 1997 Academic Press Limited.