2026-05-19T14:46:28Zhttps://keep.lib.asu.edu/oai/requestoai:keep.lib.asu.edu:node-1554482024-12-20T18:25:12Zoai_pmh:alloai_pmh:repo_items155448
https://hdl.handle.net/2286/R.I.44103
http://rightsstatements.org/vocab/InC/1.0/
All Rights Reserved
2017
xiv, 117 pages : illustrations (some color)
Doctoral Dissertation
Academic theses
Text
eng
Lu, Jing
Smith, David J.
Alford, Terry L.
Crozier, Peter A.
McCartney, Martha R.
Zhang, Yong-Hang
Arizona State University
Partial requirement for: Ph.D., Arizona State University, 2017
Includes bibliographical references
Field of study: Materials science and engineering
In this dissertation research, conventional and aberration-corrected (AC) transmission electron microscopy (TEM) techniques were used to evaluate the structural and compositional properties of thin-film semiconductor compounds/alloys grown by molecular beam epitaxy for infrared photo-detection. Imaging, diffraction and spectroscopy techniques were applied to TEM specimens in cross-section geometry to extract information about extended structural defects, chemical homogeneity and interface abruptness. The materials investigated included InAs1-xBix alloys grown on GaSb (001) substrates, InAs/InAs1-xSbx type-II superlattices grown on GaSb (001) substrates, and CdTe-based thin-film structures grown on InSb (001) substrates.<br/><br/>The InAsBi dilute-bismide epitaxial films were grown on GaSb (001) substrates at relatively low growth temperatures. The films were mostly free of extended defects, as observed in diffraction-contrast images, but the incorporation of bismuth was not homogeneous, as manifested by the lateral Bi-composition modulation and Bi-rich surface droplets. Successful Bi incorporation into the InAs matrix was confirmed using lattice expansion measurements obtained from misfit strain analysis of high-resolution TEM (HREM) images.<br/><br/>Analysis of averaged intensity line profiles in HREM and scanning TEM (STEM) images of the Ga-free InAs/InAs1-xSbx type-II strained superlattices indicated slight variations in layer thickness across the superlattice stack. The interface abruptness was evaluated using misfit strain analysis of AC-STEM images, electron energy-loss spectroscopy and 002 dark-field imaging. The compositional profiles of antimony across the superlattices were fitted to a segregation model and revealed a strong antimony segregation probability.<br/><br/>The CdTe/MgxCd1-xTe double-heterostructures were grown with Cd overflux in a dual-chamber molecular beam epitaxy with an ultra-high vacuum transfer loadlock. Diffraction-contrast images showed that the growth temperature had a strong impact on the structural quality of the epilayers. Very abrupt CdTe/InSb interfaces were obtained for epilayers grown at the optimum temperature of 265 °C, and high-resolution imaging using AC-STEM revealed an interfacial transition region with a width of a few monolayers and smaller lattice spacing than either CdTe or InSb.
Materials Science
Engineering
Nanoscience
extended defects
infrared photon detector
interface abruptness
Scanning transmission electron microscopy
spectrum imaging
Transmission Electron Microscopy
Infrared detectors
Semiconductors
Thin films
Evaluation of compound semiconductors for infrared photo-detection applications