Silicon Photonics: Fundamentals and Devices

3.1 Introduction

Most of the modern optoelectronic and photonic devices rely on heterojunctions, that is, junctions between two dissimilar semiconductors. Over the last two or three decades, nanostructures like quantum wells (QWs), quantum wires (QWRs), and quantum dots (QDs) prepared by using heterostructures are finding more and more use in realizing photonic devices. Most of the recent developments in the area of Si photonics also are made with quantum heterostructures. This chapter gives first an introduction to quantum nanostructures in general. The basic concept of quantum confinement in quantum wells, wires, and dots is first introduced and illustrated by using the conventional compound semiconductors and their alloys. Some basic electronic properties of low-dimensional systems formed in these quantum nanostructures are then discussed. The peculiarities in quantum structures made of silicon and its alloys with other group IV elements are finally pointed out.