Band Structure of HgSe and HgSe–HgTe Alloys

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Abstract
A detailed analysis of Hall coefficient data obtained at temperatures between 77° and 350°K has been made for HgSe and HgSe0.5Te0.5 samples containing excess donor concentrations up to 1019 cm−3. On the basis of previous magnetoresistance, Seebeck coefficient, and reflectivity data, a spherically symmetric non‐quadratic conduction band exhibiting the ε(k) dependence described by Kane was adopted in making the analysis. Calculations based on a conventional two‐band model failed to give quantitative agreement with experiment, but good agreement was obtained on the basis of a model in which the conduction band and one valence band overlap in energy. Therefore the materials are semimetals rather than semiconductors. The best fit to the data was obtained with an overlap energy of 0.07 ev for both HgSe and HgSe0.5Te0.5, with hole density‐of‐states masses of 0.17 m0 and 0.30 m0, respectively. With increasing carrier concentration, the optical absorption edge for heavily doped HgSe exhibits a shift to higher energies which is characteristic of n‐type materials with low electron effective masses. Qualitatively, the optical data are consistent with a semimetal band model rather than with a semiconductor model, since the interband absorption edge apparently occurs at photon energies less than the Fermi energy.

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