Electronic Applications Essay

21908 WordsDec 3, 201288 Pages
An Overview of III-V Compounds with Emphasis on InP and Its Electronic Applications -1- Chapter 1 INTRODUCTION Atom from group III of the periodic table combine with atoms from group V to from crystalline semi conducting compound. We call these semiconductors "III-V compounds". They are not alloys but definite chemical compounds with a 1:1 atomic ratio between the III and V atoms, which occupy alternate sites in the crystal lattice. For example, if we melt a mixture of indium and antimony, the compound InSb is formed, and, on solidification any excess of either constituent is thrown out as a second phase. III atoms have one valence electron less and V atoms one electron more than those atoms from group IV of the periodic table which form semiconductor crystals, e.g. diamond, germanium and silicon. III-V compounds have, therefore, the same average number of electrons per atom as the group IV Semi- conductors and it is found that the compounds indeed have a crystal structure and electronic properties which are in many ways similar to those of the group IV semiconductors. Nevertheless, III-V compound possess and characteristic properties which distinguish them from the group IV semiconductors, these difference arise chiefly from the fact that the compound crystals have a lower symmetry than the group IV crystal and that, whereas the group IV semiconductors consist of covalently bound neutral atoms, the III-V compounds contain positive and negative ions at the lattice site. The first of the III-V compounds to be reported was InP by Thiel and Koelsch [1]. Huggins [2] pointed out in 1926 that binary compound formed between group III and group V elements should crystallize in form similar to the diamond structure taken up by the group IV semiconductors, there are two kinds of atoms in the unit cell, and so they form a more general system than the group IV

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