Effect of magnetic field on excitons in bulk and heterostructure semiconductors containing disorder

A theory of exciton formation is developed for double-layer semiconductor systems in which electrons and holes are spatially separated by a potential barrier in the presence of a magnetic field. The effect of disorder due to interface roughness of the double-layer structures is included. Use is made of a lattice-gas model to calculate electron, hole, and exciton densities. Kinetic processes are neglected because they are negligible when strong disorder is present in the system. The theory is applied to type-II AlAs/GaAs quantum wells and to bulk GaAs in which electrons and holes are spatially separated. It is predicted that the formation of excitons in spatially separated electron-hole systems is enhanced by the presence of a magnetic field.