tailieunhanh - Báo cáo hóa học: " Properties and applications of quantum dot heterostructures grown by molecular beam epitaxy"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Properties and applications of quantum dot heterostructures grown by molecular beam epitaxy | Nanoscale Res Lett 2006 1 32-45 DOI s11671-006-9017-5 NANO REVIEW Properties and applications of quantum dot heterostructures grown by molecular beam epitaxy M. Henini Published online 26 July 2006 to the authors 2006 Abstract One of the main directions of contemporary semiconductor physics is the production and study of structures with a dimension less than two quantum wires and quantum dots in order to realize novel devices that make use of low-dimensional confinement effects. One of the promising fabrication methods is to use selforganized three-dimensional 3D structures such as 3D coherent islands which are often formed during the initial stage of heteroepitaxial growth in lattice-mismatched systems. This article is intended to convey the flavour of the subject by focussing on the structural optical and electronic properties and device applications of self-assembled quantum dots and to give an elementary introduction to some of the essential characteristics. Keywords Heterostructures Semiconductors Self-assembly Quantum dots Lasers Optoelectronics Introduction It is well known that quantum confinement of charge carriers arises from a potential well in the band edges when the well width typically a few hundred Angstroms is comparable to the de Broglie wavelength of the carriers. The decreased dimensionality of the free-carrier motion . confinement results in the density of states DOS of the carriers being modified. The DOS gives a measure of the maximum number of M. Henini El School of Physics and Astronomy University of Nottingham Nottingham NG7 2RD UK e-mail carriers that can occupy an energy range. The DOS due to carrier motion in the x y and z directions of the active region in a double heterostructure DH laser is schematically shown in Fig. 1 a . It can be seen that for a given band conduction band CB or valence band VB the DOS is small near the edge of the band and increases with increasing energy. By reducing the