文档介绍：Quantum-Confined Materials
Nanomaterials constitute a major area of nanophotonics
nanoscale optical materials involve a highly diverse range of nanostructure designs and cover a broad range of optical applications
By manipulation of their nanostructure, optical properties can be judiciously controlled to enhance a specific photonic function and/or introduce a new photonic manifestation as well as to allow integration of many functions to achieve multifunctionality
Quantum Wells
Quantum wells are structures in which a thin layer of a smaller bandgap semiconductor is sandwiched between two layers of a wider bandgap semiconductor
Type I quantum well
The heterojunction between the smaller and the wider bandgap semiconductors forms a potential well confining the electrons and the holes in the smaller bandgap material region.
Type II quantum well
the electrons and the holes are confined in different layers. Thus the motions of the electrons and the holes are restricted in one dimension (along the thickness direction)
Schematic of a representative quantum well, which here is the extensively studied case of AlGaAs/GaAs
Example of a type I quantum well. Left: electron (top) and hole (bottom) wavefunctions
For energies E < V, the energy levels of the electron are quantized for the direction z of the confinement; hence they are given by the model of particle in a one-dimensional box. The electronic energies in the other two dimensions (x and y) are not discrete and are given by the effective mass approximation
each quantum number n, the values of ponents kx and ky form a two-dimensional band structure. However, the wavevector kz along the confinement direction z takes on only discrete values, kz = n/l
For E > V , the energy levels of the electron are not quantized even along the z direction. The electronic energy level is a continuum. The total number of discrete levels is determined by the width l of the well and the barrier height V.
Plot of energy sub-bands f