| In this work the structural and electrical properties of the dislocation core in cubic semiconductors are investigated by ab initio, total energy electronic structure methods. A geometric technique to isolate a single partial dislocation in a cylinder of GaAs is developed and tested. The agreement between a high resolution, electron microscopy image of a 30° beta partial generated from a structure simulated using this method and an experimentally measured HREM image is found to be within 8 pm one atomic plane outside of the dislocation, and 18 pm on the defect. This level of agreement between microscopy and computation for bulk dislocations is the best recorded in the present literature.; The gap states associated with the alpha and beta partial dislocations have been measured previously, but correlating the observed state with core type has remained an open question. The states associated with the 90° and 30°, alpha and beta partials are calculated and confirm the most recent experimental measurements.; The relative energy of the single period (SP) and double period (DP) core reconstructions for the 90° partial are computed for GaAs and are found to be energetically degenerate. This is the first time that the relative energies of the two structures were examined independently for the alpha and beta dislocations.; Using a periodic cell geometry, the relative energies of the SP and DP reconstructions are calculated for C, Si, and Ge for pressures ranging between +/-3.5 GPa. It was found that for these crystals, the DP structure is preferred, and that the relative energies are insensitive to pressure. It was discovered that the relative energies of the reconstructions scale with the Kleinman parameters. This is the first time that such a trend relating the bulk crystal properties and the reconstruction energies has been proposed.; Finally, a Monte Carlo model is proposed that allows for an investigation of the interactions of reconstruction phases, kinks, and anti-phase defects on the 90° partial dislocation in diamond cubic semiconductors. |
