Characterization of Extended Defects in Heteroepitaxy of GaSb/Si Thin Films with Conventional Transmission Electron Microscopy

Abstract

<p>Research in the area of improving the efficiency and manufacturability of alternative energy technologies has been of high interest due to the growing environmental concerns of energy resources. Group III-antimonide-based compound semiconductors have been sought after as excellent candidates for photovoltaic conversion of infrared radiation, outside the spectral range absorbed by the currently available crystalline Si solar cells. The major challenge is the GaSb/Si interface is highly lattice mismatched, and inherently heterovalent. This leads to a high density of structural defects, many of which have not been investigated fully. Both optical and electrical properties of such heteroepitaxy thin films are strongly dependent on the periodicity of the crystal lattice, and the presence of extended defects cause perturbations in the lattice periodicity. Therefore the nature of such extended defects must be understood, in order to better manipulate the growth process to minimize their presence. This thesis demonstrates that through the use of conventional transmission electron microscopy, further insight can be gained into understanding the origin, distribution, propagation, and interaction of various extended defects. From this, a couple of ways to systematically suppress some of the defects have also been implemented, and the mechanism by which they induce such a suppression is also discussed.</p>