Energy band of ternary alloy semiconductors—Calculation by a coherent-potential approximation based on the method of linear combination of bond orbitals
- 1 June 1979
- journal article
- research article
- Published by AIP Publishing in Journal of Applied Physics
- Vol. 50 (6), 4143-4155
- https://doi.org/10.1063/1.326495
Abstract
A method of calculating the effect of the random distribution of atoms on the energy‐band structure of ternary alloy semiconductors is proposed, where the coherent‐potential approximation based on the method of linear combination of bond orbitals (LCBO) is used. In the case of GaAscP1−c, the nonlinear dependence of the energy upon the alloy composition c at various symmetry points within the first Brillouin zone is calculated. It is found that the effect of disorder is an important factor in explaining the bowing effect of band gaps; In particular, the magnitudes of the direct gap Γv15→Γc1, and the indirect gap Γv15→Xc1 agree well with experimental results. The energy‐band structure, including the lifetime broadening of the energy at each Bloch state, is shown for GaAs0.5P0.5. Also, the relation between the LCBO parameters and the effect of disorder on various states is qualitatively discussed. The effect of disorder on the p‐like or s‐like states of the valence band increases with increasing the difference between the p‐like or s‐like energy levels, which are represented by the bonding orbitals, of both alloy constituents. The relation between the effect of disorder on the conduction band and the antibonding orbitals is the same as the relation between the effect of disorder at the sites of group‐V atoms and that at the sites of group‐III atoms appears noticeably at the points Xc1 and Xc3 of the conduction band and at the points Xv1 and Xv3 of the valence band.Keywords
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