Quantum well and superlattice electrodes

Abstract

Publisher Summary Charge carriers in semiconductors can be confined, by potential barriers, in one spatial dimension, two spatial dimensions, or in three spatial dimensions. These regimes are termed quantum films, quantum wires, and quantum dots, respectively. Quantum films are also more commonly referred to as quantum wells. However, quantum wires and quantum dots also contain quantum wells, but differ in the dimensionality of their potential wells. One-dimensional quantum wells, hereafter called quantum films or just quantum wells, are usually formed through epitaxial growth of alternating layers of semiconductor materials, with different band gaps. A single quantum well is formed from one semiconductor sandwiched, between the two layers of a second semiconductor, having a larger band gap; the center layer with the smaller band gap semiconductor forms the quantum well, while the two layers, sandwiching the center layer, create the potential barriers. Two types of potential wells can actually be formed in the quantum well structure; one well is for conduction band electrons, the other for valence band holes. Multiple quantum well structures consist of a series of quantum wells. A multiple quantum well structure that exhibits strong electronic coupling, between the wells, is termed as superlattice. This chapter describes the various aspects of quantum well and superlattice structures, including fabrication and characterization; optical and electronic properties; the dynamics of photogenerated electrons and holes; and their behavior as electrodes in photoelectrochemical cells.