Plastic Relaxation of Highly Tensile Strained (100) Ge/InGaAs Heterostructures
dc.contributor.author | Goley, Patrick Stephen | en |
dc.contributor.committeechair | Hudait, Mantu K. | en |
dc.contributor.committeemember | Lester, Luke F. | en |
dc.contributor.committeemember | Heremans, Jean J. | en |
dc.contributor.department | Electrical and Computer Engineering | en |
dc.date.accessioned | 2015-07-30T08:00:30Z | en |
dc.date.available | 2015-07-30T08:00:30Z | en |
dc.date.issued | 2015-07-29 | en |
dc.description.abstract | Biaxial tensile strain has been shown to greatly enhance the optoelectronic properties of epitaxial germanium (Ge) layers. As a result, tensile-Ge (and#949t-Ge) layers grown on larger lattice constant InGaAs or GeSn have attracted great research interest. However, no previous studies have investigated the plastic relaxation occurring in these and#949t-Ge layers. Here, we experimentally demonstrate that plastic relaxation occurs in nearly all and#949t-Ge epitaxial layers that are of practical interest for optoelectronic applications, even when layers may still exhibit strain-enhanced characteristics. We show arrays of misfit dislocations (MDs), which are mostly disassociated, form at the and#949t-Ge/InGaAs interface for and#949t-Ge layers as thin as 15 nm with less than 1% total mismatch. Wedge geometry of plain view transmission electron microscopy (PV-TEM) foils is utilized to carry out a depth dependent investigation MD spacing for a range of and#949t-Ge/InGaAs heterostructures. MD spacing measured by PV-TEM is correlated to and#949t-Ge layer relaxation measured by high-resolution x-ray diffraction. We confirm very low relaxation (< 10% relaxed) in and#949t-Ge layers does not imply they have been coherently grown. We demonstrate plastic relaxation in the and#949t-Ge layer is acutely sensitive to grown-in threading dislocations (TDs) in the template material, and that reducing TD density is critical for maximizing strain retention. Given that and#949t-Ge layer thicknesses of 150+ nm with greater than 1% tensile strain are desired for optoelectronic devices, this work suggests that MDs may inevitably be present at and#949t-Ge/InGaAs heterointerfaces in practical devices, and that the effect of MDs on optoelectronic performance must be better understood. | en |
dc.description.degree | Master of Science | en |
dc.format.medium | ETD | en |
dc.identifier.other | vt_gsexam:6044 | en |
dc.identifier.uri | http://hdl.handle.net/10919/54944 | en |
dc.publisher | Virginia Tech | en |
dc.rights | In Copyright | en |
dc.rights.uri | http://rightsstatements.org/vocab/InC/1.0/ | en |
dc.subject | tensile | en |
dc.subject | strain | en |
dc.subject | germanium | en |
dc.subject | misfit dislocations | en |
dc.subject | stacking faults | en |
dc.subject | plastic relaxation | en |
dc.subject | elastic relaxation | en |
dc.subject | Shockley partial dislocations | en |
dc.title | Plastic Relaxation of Highly Tensile Strained (100) Ge/InGaAs Heterostructures | en |
dc.type | Thesis | en |
thesis.degree.discipline | Electrical Engineering | en |
thesis.degree.grantor | Virginia Polytechnic Institute and State University | en |
thesis.degree.level | masters | en |
thesis.degree.name | Master of Science | en |
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