EXCITON BINDING-ENERGIES IN FINITE-BARRIER TYPE-II QUANTUM-WELL STRUCTURES IN A MAGNETIC-FIELD

We have developed a variational formalism for calculations of the exciton binding energies in the GaAs-AlAs type-II quantum-well structures in the presence of a magnetic field applied along the growth axis. In contrast to some previous calculations, we take into account the finiteness of the potential barriers at the GaAs-AlAs interfaces and the mismatch of the effective masses of electron and hole across such potential barriers. The exciton wave function is expressed in terms of electron and hole subband wave functions and a multiterm Gaussian-type-orbital expansion, with variationally determined coefficients. The finite overlap of the electron and hole wave functions is found to increase exciton binding energies by up to 10-15 %, depending on thickness of the GaAs and AlAs layers. The application of the magnetic field compresses the excitonic wave functions and is found to enhance their binding energies.