Quantum effects occurring at interfaces between GaAs and AlxGa1−x As are reviewed. Electrons and holes can be confined to two-dimensional quantum states in thin semiconductor layers or at semiconductor heterointerfaces. The twodimensional states in GaAs/AlxGa1−xAs structures show strongly modified electrical and optical behavior relative to unconfined material, with the properties strongly dependent on the structural design.
Electrons confined in high mobility structures at selectively doped GaAs-AlxGa1−xAs heterointerfaces show a quantized Hall effect with an associated vanishing parallel resistance and, in high magnetic fields, an apparent electron crystallization.
Optical transitions between confined electron and hole states in quantum well thin layers form the basis of quantum well luminescence and for new non-linear optical logic structures.
All the quantum effects are sensitive to interfacial properties which are closely dependent on the conditions of epitaxial growth.