CHAPTER LIST

1.1 INTRODUCTION

Compound semiconductors which consist of various elements have widely ranging physical properties. They have therefore many possible applications. The physical properties which may vary, include bandgaps, crystal lattice structures, electron and hole mobilities, optical properties, thermal conductivity, and so on. By selecting appropriate compound semiconductor materials, it becomes possible to realize various devices which can not be achieved using the main elemental semiconductor material, silicon. It is therefore important to understand the physical properties of compound semiconductors and to know how to select appropriate materials for desired applications. Explanation of these properties can be found in speciality books. ^{1 9}

1.2 COMPOUND SEMICONDUCTORS

Among many compounds which consist of more than two elements, some show semiconductor properties. Some typical semiconductors are shown in Table 1.1. Compounds which show semiconductor properties have the following features according to Wilson's model.10

1. The conductivity of the semiconductor is electronic. Ionic conductivity is excluded.

2. Conductivity is largely increased as a function of temperature.

3. Conductivity is very dependent on the kind of impurities and their concentrations.