Contact block reduction method for ballistic transport and carrier densities of open nanostructures

A method is presented for quantum-mechanical ballistic transport calculations of realistic two- and three-dimensional open devices that may have any shape and any number of leads. Observables of the open system can be calculated with an effort comparable to a single calculation of a suitably defined closed system. The method is based on a previously developed scheme for calculating transmission functions, the contact block reduction method, and is shown to be applicable to the density matrix, the density of states, and the local carrier density. The electronic system may be characterized by a single or multiband Hamiltonian. We illustrate the method for the four-band GaAs hole transport through a two-dimensional three-terminal T-junction device and for the electron tunneling through a three-dimensional InAs quantum dot molecule embedded into an InP heterostructure.