Chapter 1 Theoretical Bases of the Optical Properties of Semiconductor Quantum Nano-Structures

Abstract

This chapter provides a theoretical background of the optical properties of semiconductor quantum nanostructures and emphasizes on how those properties vary from quantum wells to quantum dots and how they are influenced by the exciton effect. Semiconductor quantum wells in which a thin semiconductor film is sandwiched between different materials via heterojunctions confine electron motion in the two-dimensional thin-film plane. This two-dimensionality gives rise to new optical properties that are not observed in bulk materials: (1) such as optical absorption and gain spectra peculiar to the step like density of states, (2) strong exciton resonance clearly observable even at room temperature, and (3) large optical nonlinearity and an electric field-induced energy shift of the resonance, called the “quantum-confined Stark effect.” Multidimensional quantum-confinement structures, such as quantum wires and quantum dots, are expected to improve quantum-effect optical devices.