This book contains the lectures delivered at the NATO Advanced Research Workshop on the "Intersubband Transistions in Quantum Wells" held in Cargese, France, between the t 9 h and the 14th of September 1991. The urge for this Workshop was justified by the impressive growth of work dealing with this subject during the last two or three years. Indeed, thanks to recent progresses of epitaxial growth techniques, such as Molecular Beam Epitaxy, it is now possible to realize semiconductor layers ( e.g. GaAs) with thicknesses controlled within one atomic layer, sandwiched between insulating layers (e.g. AlGaAs). When the semiconducting layer is very thin, i.e. less than 15 nm, the energy of the carriers corresponding to their motion perpendicular to these layers is quantized, forming subbands of allowed energies. Because of the low effective masses in these semiconducting materials, the oscillator strengths corresponding to intersubband transitions are extremely large and quantum optical effects become giant in the 5 - 20 ~ range: photoionization, optical nonlinearities, ... Moreover, a great theoretical surprise is that - thanks to the robustness of the effective mass theory - these quantum wells are a real life materialization of our old text book one-dimensional quantum well ideal. Complex physical phenomena may then be investigated on a simple model system.

In the field of logic circuits in microelectronics, the leadership of silicon is now strongly established due to the achievement of its technology. Near unity yield of one million transistor chips on very large wafers (6 inches today, 8 inches tomorrow) are currently accomplished in industry. The superiority of silicon over other material can be summarized as follow: - The Si/Si0 interface is the most perfect passivating interface ever 2 obtained (less than 10" e y-I cm2 interface state density) - Silicon has a large thermal conductivity so that large crystals can be pulled. - Silicon is a hard material so that large wafers can be handled safely. - Silicon is thermally stable up to 1100 DegreesC so that numerous metallurgical operations (oxydation, diffusion, annealing ... ) can be achieved safely. - There is profusion of silicon on earth so that the base silicon wafer is cheap. Unfortunatly, there are fundamental limits that cannot be overcome in silicon due to material properties: laser action, infra-red detection, high mobility for instance. The development of new technologies of deposition and growth has opened new possibilities for silicon based structures. The well known properties of silicon can now be extended and properly used in mixed structures for areas such as opto-electronics, high-speed devices. This has been pioneered by the integration of a GaAs light emitting diode on a silicon based structure by an MIT group in 1985.

Optoelectronics is a practical and self-contained graduate-level text on the subject. The authors include such topics as quantum mechanics of electron-photon interaction, quantization of the electro-magnetic field, semiconductor properties, quantum theory of heterostructures and nonlinear optics. They build on these concepts to describe the physics, properties and performances of light-emitting diodes, quantum well lasers, photodetectors, optical parametric oscillators and waveguides. The emphasis is on the unifying theoretical analogies of optoelectronics, such as equivalence of quantization in heterostructure wells and waveguide modes, entanglement of blackbody radiation and semiconductor statistics.

Optoelectronics is a practical and self-contained graduate-level text on the subject. The authors include such topics as quantum mechanics of electron-photon interaction, quantization of the electro-magnetic field, semiconductor properties, quantum theory of heterostructures and nonlinear optics. They build on these concepts to describe the physics, properties and performances of light-emitting diodes, quantum well lasers, photodetectors, optical parametric oscillators and waveguides. The emphasis is on the unifying theoretical analogies of optoelectronics, such as equivalence of quantization in heterostructure wells and waveguide modes, entanglement of blackbody radiation and semiconductor statistics.