TABLE OF CONTENTS Levon V. Asryan and Serge Luryi, State University of New York at Stony Brook
The emergence of devices based on nanometer-size active elements marked the era of nanoelectronics and nanophotonics. Among such elements are notably low-dimensional heterostructures, such as QWs [1], quantum wires (QWRs) [2], and QDs [3]. Quantum confinement in low-dimensional heterostructures strongly modifies the basic properties of a semiconductor crystal.
In a QW, carriers are spatially confined in the transverse direction and move freely in its plane. In a QWR, carriers are spatially confined in two transverse directions and move freely along it. Hence, the carrier energy spectra in both QWs and QWRs are continuous within wide subbands of allowed states and, in this sense, they do not qualitatively differ from those in a bulk crystal.
In a QD, carriers are three-dimensionally confined and the modification of electronic properties is most strongly pronounced: the energy levels are discrete. For this reason, QDs are also referred to as superatoms or artificial atoms. A QD of typical size (several nanometers to several tens of nanometers) contains several thousands to several tens of thousands atoms. Quantum dots have generated much interest as a new class of human-made materials with tunable (by varying both the composition and size) energies of discrete atomic-like states.
The semiconductor laser is the fundamental device of modern optoelectronics and photonics. It was proposed long ago [4] that reducing the dimensionality of the active region could significantly improve laser performance...
