TABLE OF CONTENTS Before examining the various semiconductors it is extremely useful to examine the atomic structure of some of the elements which make up the various semiconductors.
| IV | Semiconductors |
| c | 1s 2 |
| Si | 1s 22s 22p 6 |
| Ge | ls 22 S 22 P 63l 25'3d 10 |
| III-V | Semiconductors |
| Ga | ls 22s :V3s 23p 63d 10 |
| As | l S 22 S 22p 63 S 23 P 63d 10 |
A very important conclusion can be drawn about the elements making up the semiconductors: The outermost valence electrons are made up of electrons in either the s-type or p-type orbitals. While this conclusion is strictly true for the elements in the atomic form, it turns out that even in the crystalline semiconductors the electrons in the valence and conductor band retain this s- or p-type character, even though they are "free" Bloch electrons. It is extremely important to appreciate this simple feature since it plays a key role in optical and transport processes in semiconductors.
We will now discuss several techniques for obtaining bandstructure of materials. As noted in the introduction there are methods which describe the entire bandstructure reasonably well and methods that are valid over a narrow energy range. The first technique we will discuss is the tight binding method.
The tight binding method (TBM) is an empirical technique, i.e., experimental inputs are used to fit the bandstructure. TBM...
