Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 39 for “"threading dislocation"”.
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Molecular beam epitaxy of InAsP graded buffers: From mid-infrared quantum wells to InAs virtual substrates with low threading dislocation density
… on GaAs or InP substrates, defects like threading dislocations and misfit dislocations harm the performance of these metamorphic structures. This thesis explores metamorphic growth on InP using InAsP graded buffers grown with molecular beam epitaxy. The first part of this thesis analyzes …
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Substrate and channel engineering for improving performance of strained-SiGe MOSFETs
… on the commercially developed Si platform, a low threading dislocation density SiGe platform is required. A relaxed SilGe. graded buffer creates a larger lattice constant on a Si substrate while providing low threading dislocation densities (TDD) on the order of 105 cm-2. For many III-V devices on …
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High mobility strained Si/SiGe heterostructure MOSFETs : channel engineering and virtual substrate optimization
… onto silicon substrates. In this thesis, dislocation dynamics in compositionally graded SiGe layers are explored and mobility enhancements in strained Si/SiGe metal-oxide-semiconductor field-effect transistors (MOSFETs) are evaluated. These results demonstrate the dramatic increases in …
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III-V compositionally graded buffers for heterostructure integration
… (gradual or abrupt strain introduction) on threading dislocation density, surface roughness, epi-layer relaxation, and tilt. We find that gradual introduction of strain causes increased dislocation densities (>10⁶ cm-²) and tilt of the epi-layer (> 0.10°). A method of abrupt strain …
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Design, growth and optimization of 2-μm InGaSb/AlGaSb quantum well based VECSELs on GaAs/AlGaAs DBRs.
… DBR. The challenge is therefore to reduce the threading dislocation density in the active region without a very thick metamorphic bu\u21b5er and this is achieved by inducing 90! interfacial misfit dislocation arrays between the GaSb and GaAs layers. In this work cross section transmission …
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Advanced engineered substrates for the integration of lattice-mismatched materials with silicon
… buffers are developed in this thesis. A rise in threading dislocation density was observed in high-Ge content relaxed graded SiGe layers grown at relatively high temperatures, which was attributed to dislocation nucleation. This observation is contrary to conventional graded buffer theory in …
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Growth and characterization of high quality relaxed graded silicon germanium layers for integrated photodetectors
… a high surface roughness, (ii) the formation of dislocation pile-ups, (iii) an increase in the threading dislocation density, (iv) tensile strains and micro-cracking due to thermal mismatch, and (v) particulate contamination from germane gas phase nucleation. We have grown relaxed graded SiGe/Si …
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Charakterisierung und Optimierung von (Al, Ga)N-basierten UV-Photodetektoren
In this work, the influence of dislocation density, heterostructure design and detector geometry on the electro-optic properties of AlGaN-based metal-semiconductor-metal photodetectors (MSM PD) was investigated. The focus was on the realization of Schottky-type MSM PD suitable for photodetection …
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GaAsP/InGaP heterojunction bipolar transistors for III-V on Si microelectronics
… on Si substrates via a SiGe graded buffer with a threading dislocation density of 3.7 x 106 cm-2 measured by PV-TEM and EBIC. This density is appropriate for fabrication of minority-carrier devices such as HBTs. GaAsP/InGaP HBTs were fabricated on both GaAs and Si substrates with a range of defect …
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Limited-area growth of Ge and SiGe on Si
… improve the surface morphology and reduce the dislocation density in limited-area heteroepitaxy of Ge and SiGe on Si (100) substrates. Low pressure chemical vapor deposition was investigated for two limiting cases of strain states: thin, strained, high Ge content SiGe films for transistor …
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Dislocation engineering in InAlGaAs/SiGe alloy systems for heteroepitaxial integration
… related to detrimental crystal defects like dislocations that are created in the process and require buffer layers to accommodate such defects and minimize their impact on device performance. One buffer layer scheme that is receiving widespread adoption involves the direct growth of Ge on Si. …
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Development of mid-infrared light emitting diodes to replace incandescent airfield lighting
… through the use of defect filtering layers. The threading dislocation density decreased by a factor of 6 from 2.5x10^9/cm^2 to 4x10^8/cm^2 between the bottom and top of the defect filtering layer. The edge emitting devices achieved lasing up to 200K with a characteristic temperature of 150 K. …
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Ge photodetectors for Si microphotonics
… process. This work conclusively proves that threading-dislocation densities in the Ge epilayers, measured both by plan-view transmission electron microscopy and etch-pit-density (EPD) counting, were reduced by cyclic thermal annealing. Additionally, Ge mesas with no threading dislocations as …
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Materials science and design for germanium monolithic light source on silicon
… into Ge-on-Si thin films while studying the threading dislocation behavior in n-Ge during annealing; (4) Design an external cavity Ge laser integrated with Si waveguides for a low threshold current and single mode operation. Heavy n-type doping was observed to change the Ge electronic band …
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Low pressure epitaxial growth, fabrication and characterizion of Ge-on-Si photodiodes
… surface roughness (below 2 nm) and a moderate threading dislocation density (- 107 cm-2) after an annealing process. Utilizing these Ge-on-Si films, vertically illuminated Ge-on-Si pin photodiodes are fabricated in a CMOS compatible process. The best photodiodes fabricated in this work have low …
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High-quality InP on GaAs
… carrier devices is demonstrated exhibiting a threading dislocation density of 1.2x1 06/cm2 determined by plan-view transmission electron microscopy. To further quantify the quality of this InP on GaAs, a photoluminescence (PL) structure was grown to compare the quality to bulk InP. Comparable …
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Substrate Impurity Incorporation Mitigation for Improved AlGaN/GaN-ON-Si RF Performance
… nucleation layer and Si leads to a very large threading dislocation density (TDD) within the AlN layer thereby creating a leakage path, significant electron scattering, and charge carrier trap centers. The parasitic conduction path dissipates the radio-frequency (RF) signal, which increases …
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Germanium-on-silicon virtual substrate for lateral multijunction photovoltaics
… mismatch between Si and Ge can bring about threading dislocations that can significantly impair the efficiency of solar cells. This thesis presents patterned epitaxial growth of pure Ge on Si wafer through ultra-high vacuum chemical vapor deposition that achieves low threading dislocation …
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Substrate engineering for monolithic integration of III-V semiconductors with Si CMOS technology
… for Si1-xGex virtual substrates with lower threading dislocation density (TDD) and thickness. This process, the thermally relaxed ultra-thin (TRUT) buffer process, consists of coherent growth of lattice-mismatched Si1.xGex layers, followed by post-growth annealing. Growth of TRUT buffers …
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Design of III-V Multijunction Solar Cells on Silicon Substrate
… rendering the metamorphic cell sensitive to dislocations. The focus of this work is to investigate and correlate the impact of threading dislocation density on the performance of lattice-mismatched single-junction (1J) GaAs and dual-junction (2J) InGaP/GaAs solar cells on Si substrate. …
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