Transmission Electron Microscopy Characterization of Semiconductor Interfacial Structures

The epitaxial structure and characterization of semiconductor/semiconductor interfacial systems have been studied using transmission electron microscopy as the primary investigative technique. Geometrical and elastic energy theories of epitaxy, as they relate to interfacial structure, have been reviewed to establish the framework necessary for analyzing experimental semiconductor heterostructures. The diffracted electron intensities for cross-sectional semiconductor single layer and superlattice structures have been derived based on the kinematical theory. The expression for the kinematical intensity for electron diffraction from a superlattice was observed to be analogous to the diffraction of light by a diffraction grating. The effects of surface relaxation, present in all strained-layer specimens prepared for the transmission electron microscope, have been investigated using elasticity theory. Conditions where surface relaxation effects can be ignored have also been presented. In order to quantify elastic strains at the nanometer level using high resolution electron microscopy (HREM) images, a new strain analysis technique, based on the cumulative sum of deviations (CUSUM) in lattice-fringe spacings from a target value, has been developed. This technique accurately reproduced the strain profiles in simulated and experimental HREM images and proved to be robust even in the presence of high levels of experimental noise. The above theory and techniques have been applied to three experimental systems, covering three distinct regimes of lattice mismatch (lattice mismatch ranged from -3.4% to +14.6%). These three systems were In_{1-x}Ga_ {x}Sb (0 <=q x <=q 1) single layers on (001) GaAs, rm In_{1-x}Al_{x}Sb/InSb single layers and superlattices on (001) InSb, and a 20 period AlAs/GaAs superlattice on (001) GaAs.