POINT DEFECT GENERATION DURING PLASTIC DEFORMATION OF SEMICONDUCTORS

H.S. Leipner, C.G. Hübner, R. Krause-Rehberg

Fachbereich Physik, Martin-Luther-Universität, D-06099 Halle

A systematic study of the formation of point defects during uniaxial compression was carried out in various elemental and compound semiconductors [1, 2] in dependence on different deformation conditions (strain, strain rate, deformation temperature). Vacancy-type defects were detected by means of positron annihilation, which was correlated with Fourier transformation infrared spectroscopy and photoluminescence measurements. The dislocation substructure was examined by transmission electron microscopy.

Vacancies are generated in the course of non-conservative motion of dislocations. The main process is identified as the dragging of jogs along screw dislocations and the rate of vacancy formation is estimated. A row of vacancies is not found to be stable as a result of jog dragging. The agglomeration of vacancies in close vicinity to the dislocation to voids, which are thermally stable at the deformation temperature, was proven by positron lifetime spectroscopy. The densities of the voids are very sensitive to the deformation conditions, especially to the deformation temperature. Their size includes at least ten vacancies. The thermal annealing behavior of the vacancy agglomerates is studied and, in turn, related to dislocation dynamics.

Temperature-dependent positron lifetime spectroscopy indicates the presence of dislocations acting as shallow positron traps [3]. The decomposition of the lifetime spectra provides positron lifetime components related to mono- or divacancies, in addition to the void component. The thermal stability of these vacancies gives evidence that they are not isolated defects. The defect are supposed to be bound to dislocations.

The favored model of positron capture in dislocations is thus a cascade process. The undisturbed dislocation line acts as a shallow precursor state, before the positron is trapped in a deep level related to a vacancy bound to the dislocation.

1. R. Krause-Rehberg, M. Brohl, H.S. Leipner, T. Drost, A. Polity, U. Beyer, H. Alexander: Phys. Rev. B 47 (1994) 13226.
2. R. Krause-Rehberg, H. S. Leipner, A. Kupsch, A. Polity, T. Drost: Phys. Rev. B 49 (1994) 2385
3. H.S. Leipner, C.G. Hübner, J. Krüger, R. Krause-Rehberg: Mater. Sci. Forum 258-263 (1997) 981.