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Title:Electroabsorption effects near the direct and indirect edges of germanium
Author(s):Germano, Francisco Alcides
Doctoral Committee Chair(s):Handler, Paul
Department / Program:Physics
optical absorption
fundamental edges of germanium
phonon emission
Abstract:The effect of an electric field on the optical absorption near the fundamental edge of germanium was measured, employing a-c electroabsorption techniques, from 14 to 3000K with electric fields varying from 5 x 103 V/cm to 5 x 104 V/cm. The curves of the fieldinduced differential absorption coefficient Aa exhibit oscillations which, in the case of the direct edge spectrum, are satellite oscillations related to the Franz-Keldysh leffect dear a M edge, o modified by excitonic effects; in the case of the indirect edge they are due to the electric-field-induced change in the optical absorption assisted by phonon emission and absorption. The electric field dependence of the width of the oscillations in 6a above the direct energy gap agrees with the theory derived from an effective mass approximation. Analysis of the data below the gap resulted in an effective mass of 0.022 m at room temperature and 0.024 m at the lower temperatures. The amplitude of 6a is very sensitive to the temperature, while the shape of the spectrum is almost temperature independent. From the data near the indirect edge at room temperature, the energies of the phonons which take part in the indirect absorption are determined. The effects of the longitudinal acoustical (27.7 meV) and transversal acoustical (7.3 meV) phonons are predominant.
Issue Date:1967
Genre:Dissertation / Thesis
Rights Information:1967 Francisco Alcides Germano
Date Available in IDEALS:2011-07-07
Identifier in Online Catalog:6087779

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