Phase stability and the arsenic vacancy defect in In${}_x$Ga${}_{1-x}$As

The introduction of defects, such as vacancies, into In${}_x$Ga${}_{1-x}$As can have a dramatic impact on the physical and electronic properties of the material. Here we employ ab initio simulations of quasirandom supercells to investigate the structure of In${}_x$Ga${}_{1-x}$As and then examine the energy and volume changes associated with the introduction of an arsenic vacancy defect. We predict that both defect energies and volumes for intermediate compositions of In${}_x$Ga${}_{1-x}$As differ significantly from what would be expected by assuming a simple linear interpolation of the end member defect energies/volumes.

Figure 1

Plot showing the change in the lattice parameter of In${}_x$Ga${}_{1-x}$As as a function of the $x$ calculated using DFT and the SQS supercells. Included for comparison is the experimental data of Katayama et al.,[35] Gogyunova and Fedorova,[36] Liu and Peretti,[37] and Schulz et al.[38]

Figure 2

Plot showing the atomization energy of In${}_x$Ga${}_{1-x}$As as a function of $x$.

Figure 3

Plot showing the enthalpy of mixing of In${}_x$Ga${}_{1-x}$As as a function of $x$ compared to the experimental data of Rugg et al.[40]

Figure 4

Phase diagram for the GaAs-InAs system showing the low-temperature miscibility gap. Our data are compared to the DFT-B3LYP simulations of Pentin et al.[42] and data extrapolated from the liquid-solid equilibria of Shen et al.[43]

Figure 5

Plots of the defect formation energy of a V${}_{\mathrm{As}}^0$ defect in In${}_x$Ga${}_{1-x}$As under As-rich (a) and As-poor (b) conditions. Red diamonds represent configurationally averaged formation energies at 1000 K.

Figure 6

Plot showing the formation energy of a V${}_{\mathrm{As}}^0$ defect in In${}_x$Ga${}_{1-x}$As as a function of the number of In atoms located on nearest-neighbor $4a$ lattice sites surrounding the vacancy.

Figure 7

Defect volume resulting from the introduction of a V${}_{\mathrm{As}}^0$ defect in In${}_x$Ga${}_{1-x}$As as a function of the concentration of InAs, i.e., $x$. Red diamonds represent the configurationally averaged values and blue triangles represent the mean values.