TABLE OF CONTENTS In this appendix we will discuss scattering of electrons from defect in materials. The models used here to represent alloy scattering and ionized impurity scattering can be extended to cover a variety of other defects as well.
An interesting scattering problem is the scattering of a particle from a spherically symmetric square well potential. An important application of such scattering is in the understanding of carrier transport in alloys. Alloys are used in a number of technologies and are based on a material synthesis process that can randomly mix two or more different materials. By using a mixture of materials it is possible to obtain new materials that have properties intermediate between those of the components. Ideal alloys represent a random arrangement of atoms on a lattice and, therefore, even if the lattice is periodic the potential seen by electrons is non-periodic. Thus when an electron is in an alloy, it sees a randomly varying potential. To simplify the problem the random potential is separated into a periodic potential and one with random fluctuations. We write
| (E.1) |  |
where H 0 results from the average potential of the alloy and H ? arises from the difference of the real and average potentials.
Let us consider the problem of a perfectly random alloy where the smallest physical size over which the crystal potential fluctuates randomly is the unit cell. An electron moving in the alloy A x B 1 ? x will see a random...
