Molecular dynamics study of structural, mechanical, and vibrational properties of crystalline and amorphous Gal-xInxAs alloys

Using an interaction potential scheme, molecular dynamics (MD) simulations are performed to investigate structural, mechanical, and vibrational properties of Ga1-xInxAs alloys in the crystalline and amorphous phases. For the crystalline phase we find that: (i) Ga-As and In-As bond lengths vary only slightly for different compositions; (ii) the nearest-neighbor cation-cation distribution has a broad peak; and (iii) there are two nearest-neighbor As-As distances in the As (anion) sublattice. These MD results are in excellent agreement with extended x-ray absorption fine structure and high-energy x-ray diffraction data and also with ab initio MD simulation results. The calculated lattice constant deviates less than 0.18% from Vegard's law. The calculated phonon density of states exhibits a two-mode behavior for high-frequency optical phonons with peaks close to those in binary alloys (GaAs and InAs), which agrees well with a recent Raman study. Calculated elastic constants show a significant nonlinear dependence on the composition. For the amorphous phase, MD results show that: (i) the nearest-neighbor cation-anion distribution splits into well-defined As-Ga and As-In peaks as in the crystal phase; (ii) the cation-cation distribution is similar to that in the crystal phase; and (iii) the As-As distribution is quite different from that in the crystal, having only one nearest-neighbor distance. (C) 2003 American Institute of Physics.