Challenging issues of quantum devices

Quantum effects concern carrier localization, tunneling and interference effects. They give rise to remarkable conduction properties notably negative differential conductance, special symmetry and directivity. In this paper, two classes of structures are more specially addressed involving either a lateral or a vertical transport in semiconductor heterojunctions. For the electron waveguides representative of a lateral transport, the author focuses on the necessary conditions for a high directivity in multi-port devices by means of interference patterns or symmetry breaking. For the second kind of structure, special attention is paid to resonant tunneling structures in a two-terminal configuration. Beyond the search for an efficient control of resonant tunneling currents, the author reports on figures of merit, notably for ultra-fast analog applications.