Binding energy of shallow donors in asymmetrical systems of quantum wells

The dependence of the binding energy of a shallow donor impunity on its position in an asymmetrical system of tunnel-coupled quantum wells is mainly determined by the structure of the one-electron envelope functions and the difference between the dielectric constants of the quantum-well and barrier materials. An effective technique is suggested for calculating the binding energies and envelope functions of the shallow donor states in type-I heterostructures with narrow wells and barriers. We present the results of calculations for AlxGa1-xAs-GaAs structures with two or more quantum wells without imposing any restrictions on the ratios of their sizes. (C) 1997 American Institute of Physics.