Competition between shallow-impurity and T-shaped quantum-wire states

The binding energy of an electron bound to a shallow hydrogenic impurity located in a T-shaped quantum wire is calculated within the effective-mass approximation. The three-dimensional Schrödinger equation is solved by employing a method which does not rely on expansions of basis sets of wave functions. The electron binding energy is calculated as a function of the impurity position for different quantum wires. There is a competition between the T-quantum-wire states and the shallow-impurity states. Depending on the sizes of the T structure and on the position of the impurity, the electron becomes localized at the intersection of the two wells or around the impurity.