Molecular dynamics study of structural, mechanical, and vibrational properties of crystalline and amorphous Ga1ÀxInxAs alloys

Using an interaction potential scheme, molecular dynamics ~MD! simulations are performed to investigate structural, mechanical, and vibrational properties of Ga12xInxAs 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. © 2003 American Institute of Physics. @DOI: 10.1063/1.1601691#