Chapter 1
STRUCTURAL PROPERTIES OF
SEMICONDUCTORS
1.1 INTRODUCTION
In this text we will be exploring state of the art electronic devices that drive modern informa-
tion technology. Essentially all of these devices are based on semiconductors. Semiconductor
structures have also provided the stages for exploring questions of fundamental physics. As tech-
nology advances the number of semiconductors that are used in technology steadily increases.
Indeed many innovations have arisen as a result of using new materials and their heterostruc-
tures. Thus while Si, GaAs and InP have been most widely used, other materials like InAs, GaN,
InN etc. are finding important uses as well. It is important to recognize that the ability to exam-
ine fundamental physics issues and to use semiconductors in state of the art device technologies
depends critically on the purity and perfection of the semiconductor crystal.
Semiconductor structures can operate at their potential only if they can be grown with a high
degree of crystallinity and if impurities and defects can be controlled. For high structural quality
it is essential that a high quality substrate be available. This requires growth of bulk crystals
which are then sliced and polished to allow epitaxial growth of thin semiconductor regions in-
cluding heterostructures.
In this chapter we will discuss important semiconductor crystal structures. We also discuss
strained lattice structures and the strain tensor for such crystals. Strained epitaxy and its resultant
consequences are now widely exploited in semiconductor physics. High speed SiGe devices are
based on strained systems as are InGaAs and AlGaN/GaN microwave devices.
We will start with some general properties of crystalline materials and then discuss some
specific crystal structures important for semiconductors.