Luminescence from individual dislocations in II-VI and III-V semiconductors

There is a wide range of experimental results related to dislocations in diamond, group IV, II-VI, III-V semiconducting compounds, but few of these come from isolated, well-characterized individual dislocations. We are here concerned with only those results obtained in a transmission electron microscope so that the dislocations responsible were individually imaged. The luminescence properties of the dislocations were studied by cathodoluminescence performed at low temperatures (~30K) achieved by liquid helium cooling. Both spectra and monochromatic cathodoluminescence images have been obtained, in some cases as a function of temperature.There are two aspects of this work. One is mainly of technological significance. By understanding the luminescence properties of dislocations in epitaxial structures, future non-destructive evaluation will be enhanced. The second aim is to arrive at a good detailed understanding of the basic physics associated with carrier recombination near dislocations as revealed by local luminescence properties.

Spectroscopic mode Grüneisen parameters for diamond

Room temperature measurements are reported of the first and second order Raman spectra of diamond in the hydrostatic pressure range 0-2.4 GPa. Values calculated from the data for the optic mode Grüneisen parameters have been fitted in terms of a simple lattice dynamical model for diamond involving volume dependent interatomic forces. The interpolated set of mode Grüneisen parameters are shown to be in substantial agreement with thermodynamic data. The simple model for the anharmonicity of the interatomic forces in the diamond group materials is shown to provide a qualitative explanation for the contrasting low temperature behaviour of the thermal expansion exhibited by these materials.