Optical Properties of Semiconductors: Solar Cell Materials.
Abstract
The optical properties of the semiconductors silicon and gallium arsenide have been examined by a Kramers-Kronig analysis of the available experimental measurements of the optical constants (reflectivity, extinction coefficient, index of refraction, and dielectric function) for these materials. The results include the full range of optical electronic excitations, from infrared through X-rays, and have been examined by the evaluation of various sum rules. The sum rules are well satisfied by the resulting silicon data, and the results are consistent with the various experimental measurements. There is some question concerning the data in the region of band-to-band transitions (visible and ultra-violet); the resolution must await further experimental measurements of reflectivity and/or dielectric function in this spectral range. The silicon work constitutes the first part of this report. For gallium arsenide, the sum rules analysis indicates that the available experimental measurements of the absorption of gallium and arsenic may be too small in the X-ray region at energies less than the onset of L-shell core electron excitations. Also the data is incomplete in the region just above the L-shell threshold. Comparison of the final results with various experimental measurements also indicate that the available normal-incidence reflectivity data in the region of band-to-band transitions may be inaccurate (values too small). The gallium arsenide calculation and the above mentioned problems are described in the second part of this report. The work is continuing, in an attempt to locate more experimental data and to define more closely the spectral regions where the presently available data is inaccurate. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 15, 1978
- Accession Number
- ADA060640
Entities
People
- Eugene Shiles
Organizations
- Virginia Commonwealth University