Dissertations / Theses: 'Defects, silicon'

1

Pellegrino, Paolo. "Point Defects in Silicon and Silicon-Carbide." Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3133.

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2

Cameron, Adrian Ewan. "Evolution of defects in amorphized silicon." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0014921.

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3

Gabriel, Margaret A. "Electronic defects in amorphous silicon dioxide /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/8553.

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4

Niewelt, Tim [Verfasser], Eicke [Akademischer Betreuer] Weber, and Stefan [Akademischer Betreuer] Glunz. "Lifetime-limiting defects in monocrystalline silicon." Freiburg : Universität, 2017. http://d-nb.info/1178321479/34.

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5

Adey, James. "Boron related point defects in silicon." Thesis, University of Exeter, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407270.

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6

Gower, Joanne Elizabeth. "Photoluminescence of point defects in silicon." Thesis, King's College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300758.

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7

Kortegaard, Nielsen Hanne. "Capacitance transient measurements on point defects in silicon and silicol carbide." Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-211.

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Electrically active point defects in semiconductor materials are important because they strongly affect material properties like effective doping concentration and charge carrier lifetimes. This thesis presents results on point defects introduced by ion implantation in silicon and silicon carbide. The defects have mainly been studied by deep level transient spectroscopy (DLTS) which is a quantitative, electrical characterization method highly suitable for point defect studies. The method is based on measurements of capacitance transients and both standard DLTS and new applications of the technique have been used.

In silicon, a fundamental understanding of diffusion phenomena, like room-temperature migration of point defects and transient enhanced diffusion (TED), is still incomplete. This thesis presents new results which brings this understanding a step closer. In the implantation-based experimental method used to measure point defect migration at room temperature, it has been difficult to separate the effects of defect migration and ion channeling. For various reasons, the effect of channeling has so far been disregarded in this type of experiments. Here, a very simple method to assess the amount of channeling is presented, and it is shown that channeling dominates in our experiments. It is therefore recommended that this simple test for channeling is included in all such experiments. This thesis also contains a detailed experimental study on the defect distributions of vacancy and interstitial related damage in ion implanted silicon. Experiments show that interstitial related damage is positioned deeper (0.4 um or more) than vacancy related damage. A physical model to explain this is presented. This study is important to the future modeling of transient enhanced diffusion.

Furthermore, the point defect evolution in low-fluence implanted 4H-SiC is investigated, and a large number of new defect levels has been observed. Many of these levels change or anneal out at temperatures below 300 C, which is not in accordance with the general belief that point defect diffusion in SiC requires high temperatures. This thesis also includes an extensive study on a metastable defect which we have observed for the first time and labeled the M-center. The defect is characterized with respect to DLTS signatures, reconfiguration barriers, kinetics and temperature interval for annealing, carrier capture cross sections, and charge state identification. A detailed configuration diagram for the M-center is presented.

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8

Åberg, Denny. "Capacitance Spectroscopy of Point Defects in Silicon and Silicon Carbide." Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3205.

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9

Rurali, Riccardo. "Theoretical studies of defects in silicon carbide." Doctoral thesis, Universitat Autònoma de Barcelona, 2003. http://hdl.handle.net/10803/3355.

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Cálculos de estructura electrónica han sido utilizados para el estudio de la estructura, de la difusividad y de la actividad eléctrica de defectos puntuales en carburo de silicio. En particular, se han considerado impurezas de tipo n y de tipo p, boro, nitrógeno y fósforo, juntas con defectos intrínsecos, como las vacantes del cristal.
El proceso de transient enhanced diffusion del boro ha sido estudiado y se ha propuesto una descripción microscópica del mismo: el kick-out realizado por un auto-intersticial de silicio cercano ha resultado ser el responsable de la metaestabilidad del de otra forma altamente estable boro sustitucional.
El mecanismo de difusión de la vacante de carbono y de silicio ha sido discutido y caracterizado; se ha demostrado que la vacante de carbono migra solamente a través de un mecanismo de difusión a los segundos vecinos, mientras que la vacante de silicio es metaestable con respecto a la formación del par vacante-antisito y entonces el camino de difusión será mediado por la formación de dicha configuración.
El dopaje de tipo n en las condiciones de alta dosis obtenidas con nitrógeno y/o fósforo ha sido estudiado; se ha mostrado que la formación de complejos de nitrógenos eléctricamente inactivos hace que el fósforo sea la elección mas adecuada para obtener dopaje de tipo n bajo estas condiciones.
Electronic structure calculations have been used to study the structure, the diffusivity and the electrical activity of point defects in silicon carbide. Particularly, p-type and n-type impurities have been considered, namely boron, nitrogen and phosphorus, together with intrinsic defects, specifically vacancies of the host crystal.
The transient enhanced diffusion of boron have been approached and a microscopic picture of this process have been proposed; the kick-out operated by a nearby silicon self-interstitial have turned out to be the responsible of the induced metastability of the otherwise highly stable boron substitutional.
The diffusion mechanism of the carbon and the silicon vacancy have been discussed and characterised; it has been shown that the carbon vacancy can only migrate by means of a second neighbour diffusion mechanisms, while the silicon vacancy is metastable with respect to the formation of a vacancy-antisite pair, and therefore the diffusion path will be mediated by the formation of such configuration.
The n-type high-dose doping regime obtained with nitrogen and / or phosphorus have been studied; it has been demonstrated that the formation of electrically inactive nitrogen aggregate in the high-dose regime makes phosphorus the preferred choice to achieve n-type doping under such conditions.

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10

Storasta, Liutauras. "Electrically active defects in 4H silicon carbide /." Linköping : Univ, 2003. http://www.bibl.liu.se/liupubl/disp/disp2003/tek801s.pdf.

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11

Coteau, Michele Denise de. "Impurity gettering at extended defects in silicon." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333296.

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12

Chichkine, Maxim. "Ab initio study of defects in silicon." Thesis, De Montfort University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416700.

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13

Doolittle, William Alan. "Fundamental understanding, characterization, passivation and gettering of electrically active defects in silicon." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/15710.

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14

Ramanachalam, M. Swaminathan. "Correlation of defects and electrical properties in Si and ZnO." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/19675.

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15

Cheng, Tai-Tsui. "Lattice defects in beta-silicon carbide grown on (001) silicon by CVD." Case Western Reserve University School of Graduate Studies / OhioLINK, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=case1059066080.

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16

Thomas, Sarah A. "EPR study of intrinsic near surface defects in SiC." Birmingham, Ala. : University of Alabama at Birmingham, 2009. https://www.mhsl.uab.edu/dt/2009m/thomas.pdf.

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17

Peeva, A. "Microstructural Characterization and Engineering of Defects in Silicon." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-29062.

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18

Pawlak, Bartłomiej Jan. "Investigation of defects in bulk and nanocrystalline silicon." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2004. http://dare.uva.nl/document/74571.

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19

Pascoa, Soraia Sofia. "Oxygen and related defects in Czochralski silicon crowns." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for kjemi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-27116.

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For the purpose of this thesis work, four n-type CZ silicon ingots with different crown tapered angle and shouldering area were characterized in order to understand the oxygen behavior and related defects on ingot top cuts and its influence on material lifetime. A p-type CZ silicon ingot was also characterized in order to have a reference material for comparison. Differences in lifetime between the crowns were observed and a strong correlation between the crown tapered angle and oxygen concentration and distribution was established. The crown with the higher tapered angle has the highest lifetime. In contrast, the crown with the lower crown tapered angle has the lowest lifetime. The crystal body quality can be influenced by the top ingot quality in what concerns the interstitial oxygen concentration and distribution. Thus, analyzing the early body of each ingot, it might be possible to predict the crystal body quality.

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20

Coutinho, Jose Pedro Abreu. "Oxygen-related point defects in silicon and germanium." Thesis, University of Exeter, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367379.

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21

Wagner, Thomas. "Low temperature silicon epitaxy defects and electronic properties /." [S.l. : s.n.], 2003. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10678419.

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22

Wieligor, Monika Katarzyna. "Characterization of planar defects in silicon carbide nanowires." [Fort Worth, Tex.] : Texas Christian University, 2010. http://etd.tcu.edu/etdfiles/available/etd-04292010-110338/unrestricted/Wieligor.pdf.

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23

Emiroglu, Deniz. "Dislocation related defects in silicon and gallium nitride." Thesis, Sheffield Hallam University, 2007. http://shura.shu.ac.uk/19626/.

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This thesis examines the kinetics of carrier capture and emission from dislocations in silicon (Si) and gallium nitride (GaN) using deep level transient spectroscopy (DLTS) and Laplace DLTS (LDLTS).Laplace DLTS is a powerful tool in characterising point defect related emission, but until now it has not been used extensively for investigating emission from extended defects. Using LDLTS, broad DLTS peaks arising from dislocations in Si containing oxidation-induced stacking faults (OISF) were resolved into multiple emission rates. For the first time, the change in emission rates from deep levels due to the band edge modification at dislocations was evidenced by LDLTS.Silicon can be grown virtually defect free, but dislocations may be introduced in very-large scale integration (VLSI) to act as impurity gettering centres. Additionally, the interstitial oxygen inherent in Czochralski (Cz) silicon can be made to segregate to dislocation cores by specific bending and annealing conditions to increase the mechanical hardness of wafers. This process is termed dislocation locking. In this work, Cz-Si with different amounts of oxygen at dislocation cores were characterised by DLTS and LDLTS. Results show the presence of a deep level with complex capture properties. A direct correlation is observed between the DLTS peak height of this level and the amount of oxygen at the dislocation core. Laplace DLTS was used to resolve broad DLTS peaks into numerous emission rates. The fill pulse dependency tests revealed that certain emission rates are not affected by the long range Coulomb forces due to neighbouring states. This suggests that certain emission rates contained in the broad DLTS peaks may be associated with point defects which are not in the vicinity of dislocations. In comparison to silicon, the deep level characterisation of GaN using DLTS and Laplace DLTS is still in its infancy. In this work, the application of DLTS to n-type hexagonal GaN Schottky diodes has revealed a shallow donor level, a series of deep electron traps and a thermally activated metastable hole trap. The dominant deep electron level is shown to emit around room temperature. DLTS and Laplace DLTS results indicate that this level exhibits local band-bending and is likely to arise from dislocations. Laplace DLTS of electron traps has shown that the broad DLTS emission is made up of numerous emission rates. Some of these emission rates do not exhibit fill pulse dependency and could arise from point defects in the strain field of dislocations. If the sample is heated to 600K and cooled down, the subsequent DLTS spectrum displays a dominant negative peak due to hole emission. The spectrum recovers to its original state showing only electron traps if the sample is not electrically characterised for a period of several days or a week, depending on the sample. The formation of this level results in a significant drop in carrier density. It is discussed with reference to the gallium vacancy and its complexes with oxygen donors.

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24

Peeva, A. "Microstructural Characterization and Engineering of Defects in Silicon." Forschungszentrum Rossendorf, 2003. https://hzdr.qucosa.de/id/qucosa%3A21734.

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25

Langhanki, Bertram. "Electron paramagnetic resonance of process induced defects in silicon." [S.l. : s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=96273621X.

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26

Shin, Jung H. Atwater Harry Albert. "Defects in amorphous silicon : dynamics and role on crystallization /." Diss., Pasadena, Calif. : California Institute of Technology, 1994. http://resolver.caltech.edu/CaltechETD:etd-12052007-131414.

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27

Sinno, Talid R. (Talid Rabih) 1969. "Defects in crystalline silicon : integrated atomistic and continuum modeling." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/10067.

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28

Mitromara, Niki. "Electronic properties of defects in silicon and related materials." Thesis, Sheffield Hallam University, 2008. http://shura.shu.ac.uk/20068/.

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Efforts in the current semiconductor industry are focused on the production of smaller, more efficient and inexpensive devices of higher packing density. As silicon is the dominant semiconductor implemented for the fabrication of the majority of semiconductor devices, perpetual research has focused on the improvement of its properties and the realisation of the most efficient structures. This thesis presents the electrical characterisation of two different diode structures that are important for the present and future generations of electronic devices. The first part of the thesis is focused on the electrical characterisation of Ultra-Shallow Junction (USJs) Si diodes. Both p+n and n+p USJ structures that contained different implants were examined. These were very highly doped and intended to simulate the situation where a doping well is formed after heavy doping in Si for the fabrication of transistors currently used in Complementary-Metal-Oxide-Semiconductor (CMOS) technology. The implanted USJ diodes were provided by NXP, Belgium and contact deposition was performed before their electrical characterisation as part of this project. Subsequently the p+n and n+p USJ diodes were characterised by the use of Capacitance-Voltage (CV), Current-Voltage (IV), Deep Level Transient Spectroscopy (DLTS) and high resolution Laplace DLTS (LDLTS). DLTS and LDLTS are very powerful spectroscopic techniques for the profiling of defects in the bandgap of a semiconductor as well as for the identification of the electrical signatures of these defects. Transient-Enhanced Diffusion (TED) related defects were detected in these diodes as the presence of mainly carbon-related interstitial complexes was observed. In addition, certain vacancy or vacancy-dopant related levels were also discerned. The second part of this thesis presents the electrical characterisation from Schottky p-diamond/p-Si and p-diamond/n-Si p-n diodes. These diodes were readily provided, grown by the Chemical Vapour Deposition (CVD) technique, for the electrical characterisation that was performed as part of this project. The purpose of characterising both Schottky and p-n diamond on Si diodes was to detect defects near the surface of the films and near the interface with Si and hence provide a comparison between defects present at the beginning and end of growth. More defects were found near the interface with Si and the majority of observed defects were related to extended defects while the presence of grain boundaries in polycrystalline diamond was discussed.

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29

Norman, Carl Edward. "Quantitative conductive mode SEM investigations of defects in silicon." Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/46473.

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30

Fuchs, Franziska [Verfasser], and Vladimir [Gutachter] Dyakonov. "Optical spectroscopy on silicon vacancy defects in silicon carbide / Franziska Fuchs. Gutachter: Vladimir Dyakonov." Würzburg : Universität Würzburg, 2016. http://d-nb.info/1112040560/34.

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31

Ewels, Christopher Paul. "Density functional modelling of point defects in semiconductors." Thesis, University of Exeter, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388588.

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32

Olivier, Ezra Jacobus. "Analysis of the extended defects in 3C-SiC." Thesis, Nelson Mandela Metropolitan University, 2008. http://hdl.handle.net/10948/730.

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The dissertation focuses on the analysis of the extended defects present in as-grown and proton bombarded β-SiC (annealed and unannealed) grown by chemical vapour deposition (CVD) on (001) Si. The proton irradiation was done to a dose of 2.8 × 1016 protons/cm2 and the annealing took place at 1300°C and 1600°C for 1hr. The main techniques used for the analysis were transmission electron microscopy (TEM) and high resolution TEM (HRTEM). From the diffraction study of the material the phase of the SiC was confirmed to be the cubic beta phase with the zinc-blende structure. The main defects found in the β- SiC were stacking faults (SFs) with their associated partial dislocations and microtwins. The SFs were uniformly distributed throughout the foil. The SFs were identified as having a fault vector of the type 1/3 <111> with bonding partial dislocations of the type 1/6 <121> by using image simulation. The SFs were also found to be predominantly extrinsic in nature by using HRTEM analysis of SFs viewed edge-on. Also both bright and dar-field images of SFs on inclined planes exhibited symmetrical and complementary fringe contrast images. This is a result of the anomalous absorption ratio of SiC lying between that of Si and diamond. The analysis of the annealed and unannealed irradiated β-SiC yielded no evidence of radiation damage or change in the crystal structure of the β-SiC. This confirmed that β-SiC is a radiation resistant material. The critical proton dose for the creation of small dislocation loops seems to be higher than for other compound semiconductors with the zinc-blende structure.

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33

WANG, PING. "CHARACTERIZATION OF SILICON-ON-INSULATOR STRUCTURES FORMED BY ION IMPLANTATION OF OXYGEN (SILICON, DEFECTS, INSULATOR)." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183849.

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Silicon-on-insulator (SOI) structures formed in the top region of silicon wafers by ion implantation of oxygen were characterized by RBS (Rutherford Backscattering Spectrometry), OPM (Optical Microscopy), SEM (Scanning Electron Microscopy), and TEM (Transmission Electron Microscopy). Specimens taken from these wafers were previously subjected to specific thermal treatment and silicon epitaxial growth. The results of this investigation show that homogeneous, stoichiometric buried SiO₂ layers were formed beneath the silicon wafer surfaces after high-dose oxygen ion implantation (2.0 x 10¹⁸ O⁺/cm², 180 keV/O⁺). No buried SiO₂ layers were observed in the low-dose wafers (1.0 x 10¹⁷ O⁺/cm², 180 keV/O⁺). Solid-phase epitaxial regrowth (SPE) is strongly temperature dependent. The transition from amorphous (caused by ion impact) to crystalline through the SPE process is completed in the high-dose-rate wafers (∼33 μA/cm²), but not in the low-dose-rate wafers (∼17 μA/cm²). Polysilicon layers were formed on both sides of the SiO₂ layer in the low-dose-rate wafers. Evidence shows that both post annealing (>1000°C, 2 hours in N₂) and in-situ annealing (wafer substrate heating at 500°C during oxygen ion implantation) lower the imperfection density of the top surface region of silicon wafers. A silicon epitaxial layer with low levels of crystalline imperfections was able to be grown on these annealed wafers. The results also show that in-situ annealing is more effective than post annealing. The major microdefects in SOI structures observed in this investigation are dislocations.

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34

Leonard, Simon. "An investigation into metallic impurities in silicon for solar cells." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/an-investigation-into-metallic-impurities-in-silicon-for-solar-cells(4519e1a6-56bc-47ee-ac13-9459470a86ac).html.

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Photovoltaics is an exciting area of research with the potential to completely change the world's energy landscape. Silicon still dominates the photovoltaics market and shows no sign of being overtaken by other materials systems for large scale manufacture. Huge strides have been made in recent years to reduce the cost of solar modules, mainly through the introduction of mass production solar panel plants. However producing very pure single crystalline silicon is still a relatively expensive, energy intensive process. If cheaper less pure silicon could be cast into multi-crystalline ingots, without significant losses to the conversion efficiency this could be a game changer in the photovoltaics industry. For this to happen we need to have greater knowledge and understanding of the role of metallic impurities in solar silicon. If we can find ways to passivate or getter these impurities in cost effective processes that lend themselves to mass production then this would be the key to cost effective solar energy. In the work in this thesis I have investigated some of the most common and most harmful metallic impurities in silicon solar cells using a combination of Deep Level Transient Spectroscopy (DLTS), Capacitance Voltage (CV) measurements, Secondary Ion Mass Spectroscopy and Tunnelling Electron Microscopy (TEM). The specific transition metals I studied were iron, as it is one of the most common impurities and also titanium and molybdenum, because they are very harmful, have slow diffusivities and hard to get rid of with traditional gettering techniques. I have then looked at using hydrogen to electrically passivate these defects, and show evidence that hydrogen passivation is possible for interstitially incorporated titanium in silicon, but is unlikely to happen for interstitially incorporated iron. Another important part of this thesis was the observation and characterisation of molybdenum nano-precipitates in silicon. We have observed the nano-precipitates both electrically in DLTS, and physically in TEM. The precipitates have very interesting electrical properties, and appear to be very strong minority carrier recombination centres, which would have a very negative effect on solar cell performance. It is possible that these nano-precipitates could form from any of the slow diffusing transition metals, and could be a key reason to explain the efficiency gap between low purity cast silicon and high purity single crystal silicon.

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35

Ayres, J. R. A. "Electrically active defects associated with dislocations and grain boundaries in silicon." Thesis, University of Sussex, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307235.

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36

Steingrube, Silke [Verfasser]. "Recombination models for defects in silicon solar cells / Silke Steingrube." Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2011. http://d-nb.info/1015460577/34.

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37

Roth, Thomas. "Analysis of electrically active defects in silicon for solar cells /." München : Dr. Hut, 2009. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=017538840&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.

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38

Blood, Arabella M. "A study of the electrical properties of defects in silicon." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298320.

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39

Wagner, Thomas [Verfasser]. "Low temperature silicon epitaxy : Defects and electronic properties / Thomas Wagner." Aachen : Shaker, 2003. http://d-nb.info/1179037057/34.

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40

Recht, Daniel. "Energetic Beam Processing of Silicon to Engineer Optoelectronically Active Defects." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10305.

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This thesis explores ways to use ion implantation and nanosecond pulsed laser melting, both energetic beam techniques, to engineer defects in silicon. These defects are chosen to facilitate the use of silicon in optoelectronic applications for which its indirect bandgap is not ideal. Chapter 2 develops a kinetic model for the use of point defects as luminescence centers for light-emitting diodes and demonstrates an experimental procedure capable of high-throughput screening of the electroluminescent properties of such defects. Chapter 3 discusses the dramatic change in optical absorption observed in silicon highly supersaturated (i.e., hyperdoped) with the chalcogens sulfur, selenium, and tellurium and reports the first measurements of the optical absorption of such materials for photon energies greater than the bandgap of silicon. Chapter 3 examines the use of silicon hyperdoped with chalcogens in light detectors and concludes that while these devices display strong internal gain that is coupled to a particular type of surface defect, hyperdoping with chalcogens does not lead directly to measurable sub-bandgap photoconductivity. Chapter 4 considers the potential for Silicon to serve as the active material in an intermediate-band solar cell and reports experimental progress on two proposed approaches for hyperdoping silicon for this application. The main results of this chapter are the use of native-oxide etching to control the surface evaporation rate of sulfur from silicon and the first synthesis of monocrystalline silicon hyperdoped with gold.
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41

Martsinovich, Natalia. "Theory of defects arising from hydrogen in silicon and diamond." Thesis, University of Sussex, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409286.

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42

Hourahine, Benjamin. "A first principles study of hydrogen related defects in silicon." Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324743.

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43

Ferreira-Resende, Antonio Luis Santos. "An ab initio study of deep-level defects in silicon." Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312440.

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44

Harding, Ruth Emma. "Ion implantation defects in silicon studied using the photluminescence technique." Thesis, King's College London (University of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414828.

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45

Johnson, Fiona Jane. "Electron microscopy and luminescence study of defects in semiconductor silicon." Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279773.

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46

Roth, Thomas. "Analysis of electrically active defects in silicon for solar cells." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:352-opus-72668.

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47

Berney, Needleman David. "Performance limits of silicon solar cells due to structural defects." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104133.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 97-107).
To minimize the risk of catastrophic climate change, about ten terawatts of photovoltaics must be deployed in the next fifteen years. Reaching this target will require dramatic reductions in the cost and capital intensity of manufacturing photovoltaic modules coupled with a significant increase in module efficiency. The majority of the factory and equipment costs to produce the crystalline silicon modules that account for over 90% of modules sold today are for production of silicon wafers. While lower-cost wafers can be produced with cheaper equipment, the efficiency of modules incorporating these wafers is limited by the presence of structural defects, like grain boundaries and dislocations, that are absent from more expensive alternatives. This thesis presents a methodology to quantify the technology innovations necessary to reach climate-driven deployment targets for photovoltaics and shows an analysis based on current commercial technology incorporating monocrystalline silicon absorbers. Then, a model for the electrical activity of dislocations and grain boundaries and a methodology for incorporating this model into technology computer aided design (TCAD) simulations of high-efficiency solar cells are presented. The model and method are validated by comparison to analysis of the material properties and device performance of silicon solar cells containing structural defects. TCAD simulations across a wide range of defect concentrations and distributions are used to determine the material requirements for low-cost silicon containing structural defects to approach the performance of expensive, structural defect-free silicon in several high-efficiency solar cell architectures. Aspects of device design that mitigate the impact of these defects, notably higher injection-levels of electronic carriers, are identified.
by David Berney Needleman.
Ph. D.

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48

Patel, Neil Sunil. "Understanding defects in germanium and silicon for optoelectronic energy conversion." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104110.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2016.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages [143]-155).
This thesis explores bulk and interface defects in germanium (Ge) and silicon (Si) with a focus on understanding the impact defect related bandgap states will have on optoelectronic applications. Optoelectronic devices are minority carrier devices and are particularly sensitive to defect states which can drastically reduce carrier lifetimes in small concentrations. We performed a study of defect states in Sb-doped germanium by generation of defects via irradiation followed by subsequent characterization of electronic properties via deep-level transient spectroscopy (DLTS). Cobalt-60 gamma rays were used to generate isolated vacancies and interstitials which diffuse and react with impurities in the material to form four defect states (E₃₇, E₃₀, E₂₂, and E₂₁) in the upper half of the bandgap. Irradiations at 77 K and 300 K as well as isothermal anneals were performed to characterize the relationships between the four observable defects. E₃₇ is assigned to the Sb donor-vacancy associate (E-center) and is the only vacancy containing defect giving an estimate of 2 x 10¹¹ cm-³ Mrad-¹ for the uncorrelated vacancy-interstitial pair introduction rate. E₃₇ decays by dissociation and vacancy diffusion to a sink present in a concentration of 10¹² cm-³. The remaining three defect states are interstitial associates and transform among one another. Conversion ratios between E₂₂, E₂₁, and E₃₀ indicate that E₂₂ likely contains two interstitials. The formation behavior of E₂₂ after irradiation in liquid nitrogen indicates that E₃₀ is required for formation of E₂₂. Eight defect states previously unseen after gamma irradiation were observed and characterized after irradiation by alpha and neutron sources. Their absence after gamma irradiation indicates that defect formation requires collision cascades. We demonstrate electrically pumped lasing from Ge epitaxially grown on Si. Lasing is observed over a ~200nm bandwidth showing that this system holds promise for low-cost on-chip communications applications via silicon microphotonics. The observed large threshold currents are determined to be largely a result of recombination due to threading dislocations. We estimate that recombination by threading dislocations becomes negligible when threading dislocation density is by Neil Sunil Patel.
Ph. D.

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49

Danga, Tariro. "Electrical characterization of silicide and process induced defects in silicon." Diss., University of Pretoria, 2015. http://hdl.handle.net/2263/53484.

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Metal deposition on Si has effects that may be detrimental to device operation such as diffusion, Fermi level pinning and silicide formation. Silicide formation is dependent on type of metal and temperature at which particular silicide is formed. Different defects have been observed during metallisation of Si to form electrical contact. The electrical characterisation of platinum silicides and palladium silicides were investigated using current-voltage and capacitance voltage measurements. Defects introduced were characterised by deep level transient spectroscopy (DLTS) and Laplace DLTS (L-DLTS) while silicidation process was monitored by Rutherford backscattering spectroscopy (RBS). The Rutherford utilities manipulation program (RUMP) and Genplot program were used to analyse the data from RBS. The electron beam deposition process was used to fabricate Pt Schottky contacts onto n-Si (111). Subsequently these contacts were annealed at temperatures varying from 50°C to 600°C for ten minutes at each temperature. The forward I-V characteristics show that the diodes were stable at lower voltages and suffer series resistance effects at voltages higher than 0.5 V. The reverse I-V curves shows increasing leakage current with increasing annealing temperature. At lower annealing temperatures, the reverse leakage current is constant at about 10-9 A. The ideality factor increased from 1.02 to 2.61 while the barrier height decreased from 0.80 to 0.70 eV as the annealing temperature increased. DLTS revealed that electron beam deposition introduced defects which were identified as the E-centre (VP centre), the A-centre (VO centre), the interstitial carbon (Ci) and the interstitial carbon-substitutional carbon (CiCs) pair. Isochronal annealing at 10 minutes intervals revealed that the E-centre vanishes between 125 and 175°C annealing while the concentration of the A-centre increased in this range. The A-centre annealed out above 350°C and after 400°C, all the electron beam induced defects were all removed. Palladium Schottky contacts were fabricated on epitaxially grown n-Si (111) by resistive deposition. Current-voltage (I-V), capacitance- voltage (C-V) measurement techniques were used to characterise the as deposited and annealed Pd/n-Si Schottky contacts. These contacts were annealed at temperatures ranging from 200°C to 700°C, in steps of 100°C for ten minutes each temperature. The ideality factor increased from 1.2 for as deposited to 1.6 after annealing at 700°C while the Schottky barrier height (SBH) decreased from 0.69 to 0.64 eV as the annealing temperature increased. In this study, silicides seem to form at 300°C where the ideality factor is at its lowest value and SBH begins to lower. The Rutherford backscattering Spectroscopy (RBS) technique was used to verify temperatures at which Pd2Si was formed. The results obtained suggest that the Pd2Si silicide phase begins to form at 200°C and at 300°C it is completely formed. The defects introduced in epitaxially grown p-type silicon (Si) during electron beam exposure were electrically characterised using deep level transient spectroscopy (DLTS) and high resolution Laplace-DLTS. In this process, Si samples were first exposed to the conditions of electron beam deposition (EBD) without metal deposition. This is called electron beam exposure (EBE). After 50 minutes of EBE, aluminium (Al) and nickel (Ni) Schottky contacts were fabricated using the resistive deposition method. For the Al contacts, the defect level H(0.33) was identified as the interstitial carbon (????) related defect. The defect level observed using the Ni contacts had an activation energy of H(0.55). This defect has an activation energy similar to that of the I-defect. DLTS depth profiling revealed that H(0.33) and H(0.55) could be detected up to a depth of 1.2??m and 0.8??m respectively. We found that exposing the samples to EBD conditions without metal deposition introduced a different group of defects which are not introduced by the EBD method.
Dissertation (MSc)--University of Pretoria, 2015.
Physics
MSc
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50

Grillot, Patrick N. "Defects induced by strain-relaxation in heteroepitaxial germanium-silicon alloys /." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487935958846594.

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