Optical Properties and Electronic Structure of Amorphous Semiconductors
Optical properties of amorphous solids are of considerable interest since glasses of various kinds are very important optical materials. We shall treat in this chapter an example of the absorption spectrum of amorphous material which is particularly simple. We chose amorphous germanium for this study and compared its optical properties with the well-known properties of its crystalline form. The atomic arrangement in amorphous Ge was investigated by X-ray diffraction . The results of these studies can be interpreted in two ways; it is at present impossible to decide between them. In one model amorphous Ge is pictured as composed of small crystallites with linear dimensions of the order 10 Å. In the other model amorphous Ge is considered as a homogeneous medium. The tetrahedra are still the basic units of the structure but the neighboring tetrahedra are irregularly rotated so that the long-range order is lost after several atomic distances. For the interpretation of the optical properties we shall use the latter model here, but the former model would give similar results. We shall show what information concerning the changes of the electronic structure due to the loss of the long-range order can be deduced from the changes observed in the optical properties. This chapter is based on work performed jointly in the Institute of Solid State Physics in Prague and the Institute of Physics in Bucharest and reported elsewhere [1–3].
KeywordsWave Function Valence Band Absorption Edge Brillouin Zone Amorphous State
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- 2.R. Grigorovici, N. Croitoru, A. Dévényi, and E. Teleman,Proc. Seventh Conf. Phys. Semicond., Paris, 1964, Dunod (Paris), 1964, p. 423.Google Scholar
- 3.J. Tauc, A. Abraham, L. Pajasova, R. Grigorovici, and A. Vancu,Proc. Intern. Conf. Phys. of Noncrystalline Solids, Delft, 1964, North-Holland Publishing Company (Amsterdam), 1965, p. 606.Google Scholar
- 5.J. Tauc, R. Grigorovici, and A. Vancu, J. Phys. Soc. Japan (Suppl.) 21: 123 (1966).Google Scholar
- 7.A. I. Gubanov, Quantum Electron Theory of Amorphous Conductors, Consultants Bureau (New York), 1965.Google Scholar
- 11.J. Tauc, Progr. Semicond. 9: 87 (1965).Google Scholar
- 13.R. Grigorovici and A. Vancu (to be published).Google Scholar