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Optical properties and energy gap of GeTe from reflectance studies
Author(s) -
Lewis J. E.
Publication year - 1973
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220590138
Subject(s) - band gap , effective mass (spring–mass system) , germanium , materials science , valence (chemistry) , tellurium , spectral line , analytical chemistry (journal) , absorption (acoustics) , free carrier absorption , amorphous solid , free carrier , wavelength , absorption spectroscopy , optics , chemistry , optoelectronics , crystallography , physics , silicon , chromatography , quantum mechanics , astronomy , organic chemistry , metallurgy , composite material
The reflectance spectra of bulk samples of the germanium telluride (GeTe) system have been measured in the wavelength range 13 to 0.2 μm. The principal optical constants of the system have been obtained by inverting the spectra using the Kramers‐Kronig technique. Two distinct types of behavior were encountered depending on whether or not a sample exhibited a free carrier absorption peak. Samples rich in germanium lacked such a peak and had optical properties very similar to amorphous GeTe films. Tellurium rich samples always showed a large free carrier peak and from analysis of their optical Constants the effective mass and optical energy gap of the system was obtained. The variation of the effective mass and energy gap with composition (i.e., hole carrier density) is consistent with the existence of two sets of valence‐conduction bands in the system. A multiple band model based on experimental and theoretical data is outlined and its parameters are found to be in good agreement with published work.