Дисертації з теми "Nitrides of the III group"
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1
Kucheyev, Sergei Olegovich. "Ion-beam processes in group-III nitrides." View thesis entry in Australian Digital Theses Program, 2002. http://thesis.anu.edu.au/public/adt-ANU20030211.170915/index.html.
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2
Kucheyev, Sergei Olegovich, and kucheyev1@llnl gov. "Ion-beam processes in group-III nitrides." The Australian National University. Research School of Physical Sciences and Engineering, 2002. http://thesis.anu.edu.au./public/adt-ANU20030211.170915.
Повний текст джерелаАнотація:
Group-III-nitride semiconductors (GaN, InGaN, and AlGaN) are important for the fabrication of a range of optoelectronic devices (such as blue-green light emitting diodes, laser diodes, and UV detectors) as well as devices for high-temperature/high-power electronics. In the fabrication of these devices, ion bombardment represents a very attractive technological tool. However, a successful application of ion implantation depends on an understanding of the effects of radiation damage. Hence, this thesis explores a number of fundamental aspects of radiation effects in wurtzite III-nitrides. Emphasis is given to an understanding of (i) the evolution of defect structures in III-nitrides during ion irradiation and (ii) the influence of ion bombardment on structural, mechanical, optical, and electrical properties of these materials.
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Structural characteristics of GaN bombarded with keV ions are studied by Rutherford backscattering/channeling (RBS/C) spectrometry and transmission electron microscopy (TEM). Results show that strong dynamic annealing leads to a complex dependence of the damage buildup on ion species with preferential surface disordering. Such preferential surface disordering is due to the formation of surface amorphous layers, attributed to the trapping of mobile point defects by the GaN surface. Planar defects are formed for a wide range of implant conditions during bombardment. For some irradiation regimes, bulk disorder saturates below the amorphization level, and, with increasing ion dose, amorphization proceeds layer-by-layer only from the GaN surface. In the case of light ions, chemical effects of implanted species can strongly affect damage buildup. For heavier ions, an increase in the density of collision cascades strongly increases the level of stable implantation-produced lattice disorder. Physical mechanisms of surface and bulk amorphization and various defect interaction processes in GaN are discussed.
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Structural studies by RBS/C, TEM, and atomic force microscopy (AFM) reveal anomalous swelling of implanted regions as a result of the formation of a porous structure of amorphous GaN. Results suggest that such a porous structure consists of N$_{2}$ gas bubbles embedded into a highly N-deficient amorphous GaN matrix. The evolution of the porous structure appears to be a result of stoichiometric imbalance, where N- and Ga-rich regions are produced by ion bombardment. Prior to amorphization, ion bombardment does not produce a porous structure due to efficient dynamic annealing in the crystalline phase.
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The influence of In and Al content on the accumulation of structural damage in InGaN and AlGaN under heavy-ion bombardment is studied by RBS/C and TEM. Results show that an increase in In concentration strongly suppresses dynamic annealing processes, while an increase in Al content dramatically enhances dynamic annealing. Lattice amorphization in AlN is not observed even for very large doses of keV heavy ions at -196 C. In contrast to the case of GaN, no preferential surface disordering is observed in InGaN, AlGaN, and AlN. Similar implantation-produced defect structures are revealed by TEM in GaN, InGaN, AlGaN, and AlN.
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The deformation behavior of GaN modified by ion bombardment is studied by spherical nanoindentation. Results show that implantation disorder significantly changes the mechanical properties of GaN. In particular, amorphous GaN exhibits plastic deformation even for very low loads with dramatically reduced values of hardness and Young's modulus compared to the values of as-grown GaN. Moreover, implantation-produced defects in crystalline GaN suppress the plastic component of deformation.
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The influence of ion-beam-produced lattice defects as well as a range of implanted species on the luminescence properties of GaN is studied by cathodoluminescence (CL). Results indicate that intrinsic lattice defects mainly act as nonradiative recombination centers and do not give rise to yellow luminescence (YL). Even relatively low dose keV light-ion bombardment results in a dramatic quenching of visible CL emission. Postimplantation annealing at temperatures up to 1050 C generally causes a partial recovery of measured CL intensities. However, CL depth profiles indicate that, in most cases, such a recovery results from CL emission from virgin GaN, beyond the implanted layer, due to a reduction in the extent of light absorption within the implanted layer. Experimental data also shows that H, C, and O are involved in the formation of YL. The chemical origin of YL is discussed based on experimental data.
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Finally, the evolution of sheet resistance of GaN epilayers irradiated with MeV light ions is studied {\it in-situ}. Results show that the threshold dose of electrical isolation linearly depends on the original free electron concentration and is inversely proportional to the number of atomic displacements produced by the ion beam. Furthermore, such isolation is stable to rapid thermal annealing at temperatures up to 900 C. Results also show that both implantation temperature and ion beam flux can affect the process of electrical isolation. This behavior is consistent with significant dynamic annealing, which suggests a scenario where the centers responsible for electrical isolation are defect clusters and/or antisite-related defects. A qualitative model is proposed to explain temperature and flux effects.
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The work presented in this thesis has resulted in the identification and understanding of a number of both fundamental and technologically important ion-beam processes in III-nitrides. Most of the phenomena investigated are related to the nature and effects of implantation damage, such as lattice amorphization, formation of planar defects, preferential surface disordering, porosity, decomposition, and quenching of CL. These effects are often technologically undesirable, and the work of this thesis has indicated, in some cases, how such effects can be minimized or controlled. However, the thesis has also investigated one example where irradiation-produced defects can be successfully applied for a technological benefit, namely for electrical isolation of GaN-based devices. Finally, results of this thesis will clearly stimulate further research both to probe some of the mechanisms for unusual ion-induced effects and also to develop processes to avoid or repair unwanted lattice damage produced by ion bombardment.
3
Kraeusel, Simon. "Native defects in the group III nitrides." Thesis, University of Strathclyde, 2013. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=19541.
Повний текст джерелаАнотація:
The promise of the broad range of direct band gaps of the (Al,Ga,In)N system is limited by the crystal quality of current material. As grown defect densities of InN, when compared with the more mature GaN, are extremely high and InN is strongly influenced by these defects. This is particularly important due to the unusual position of the charge neutrality level of InN, leading to both the well known surface charge accumulation and difficulties in p-type doping. While impurities and native defects clearly impact on the bulk carrier density in InN, the effects of threading dislocations on the electrical properties are still in dispute. Issues such as whether the dislocation line is charged or contains dangling bonds remain open. In this work an empirical Stillinger-Weber inter-atomic potential method is employed in a systematic global search for possible dislocation core reconstructions for screw and edge dislocations in GaN. The global optimisation of the dislocation cores is performed for a wide variety of core stoichiometries ranging from Ga rich to N rich. The most promising optimised core configurations are subsequently investigated using density functional theory for GaN and InN, in order to discuss relative stability under a wide range of growth conditions and their influence on the electronic properties of the bulk material.
4
Jeffs, Nicholas James. "Growth and structural characterisation of group III nitrides." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311764.
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5
Steinhoff, Georg. "Group III-nitrides for bio- and electrochemical sensors." kostenfrei, 2008. http://mediatum2.ub.tum.de/doc/646548/646548.pdf.
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6
Seetoh, Ian Peiyuan. "Commercialization of group III nitrides-on-silicon technologies." Thesis, Massachusetts Institute of Technology, 2010. https://hdl.handle.net/1721.1/122862.
Повний текст джерелаАнотація:
Thesis: M. Eng., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2010Cataloged from PDF version of thesis.
Includes bibliographical references (pages 35-39).
While group Ill nitride materials have been commercialized for many years, there is recent interest in growing these materials on silicon substrates as a cost effective alternative to more expensive sapphire and silicon carbide technologies. Therefore, it is necessary to determine how group Ill nitride-on-silicon technologies can be positioned in way for them to be effective in their respective applications, thereby enabling their commercialization. This thesis is a systematic evaluation of the epitaxial growth on silicon carbide, sapphire and silicon substrates, focusing on their lattice-mismatches, thermal expansion mismatches, and thermal conductivity. The subsequent analysis of important commercial applications determined that GaN-on-Si technology is ready for commercialization in the near future. These applications include the InGaN/GaN white light emitting diode and the blue laser diode, as well as the AIGaN/GaN high electron mobility transistor, each with its own unique requirements for the technology and the implementation. It was recommended that start-up firms interested in commercializing GaN-on- Si technology focus on the growth of GaN on silicon substrates and engage device manufacturers proactively. InN and In-rich nitrides can complement maturing GaN and Ga-rich nitrides technologies, resulting in new applications and products in future. While the growth of InN films is currently very challenging, it is believed that the experience and revenue obtained from the commercialization of GaN-on-Si technology can benefit InN-on-Si technology, speeding up the latter's commercialization. A brief business strategy aimed at translating the findings into a feasible approach for commercialization is also provided.
by Ian Peiyuan Seetoh.
M. Eng.
M.Eng. Massachusetts Institute of Technology, Department of Materials Science and Engineering
7
Kench, P. J. "Microstructures of group III-nitrides after implantation with gallium." Thesis, University of Surrey, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343459.
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Böttcher, Tim. "Heteroepitaxy of group-III nitrides for the application in laser diodes." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965575160.
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Mudie, Stephen. "Characterisation of Group III nitrides using hard X-ray synchrotron radiation." Monash University, School of Physics and Materials Engineering, 2004. http://arrow.monash.edu.au/hdl/1959.1/9729.
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10
Khanderi, Jayaprakash. "Group-III Nitrides contribution to precusor chemistry, MOCVD, nanostructures and multiscale simulation studies /." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=979863538.
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11
Schmidtling, Torsten. "MOVPE growth and characterization of group-III nitrides using in-situ spectroscopic ellipsometry." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=981209068.
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Lymperakis, Liverios. "Ab-initio based multiscale calculations of extended defects in and on group III-nitrides." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=97581284X.
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13
Durkaya, Göksel. "Nanoscopic Investigation of Surface Morphology of Neural Growth Cones and Indium Containing Group-III Nitrides." Digital Archive @ GSU, 2009. http://digitalarchive.gsu.edu/phy_astr_diss/43.
Повний текст джерелаАнотація:
This research focuses on the nanoscopic investigation of the three-dimensional surface morphology of the neural growth cones from the snail Helisoma trivolvis, and InN and InGaN semiconductor material systems using Atomic Force Microscopy (AFM). In the analysis of the growth cones, the results obtained from AFM experiments have been used to construct a 3D architecture model for filopodia. The filopodia from B5 and B19 neurons have exhibited different tapering mechanisms. The volumetric analysis has been used to estimate free Ca2+ concentration in the filopodium. The Phase Contrast Microscopy (PCM) images of the growth cones have been corrected to thickness provided by AFM in order to analyze the spatial refractive index variations in the growth cone. AFM experiments have been carried out on InN and InGaN epilayers. Ternary InGaN alloys are promising for device applications tunable from ultraviolet (Eg[GaN]=3.4 eV) to near-infrared (Eg [InN]=0.7 eV). The real-time optical characteristics and ex-situ material properties of InGaN epilayers have been analyzed and compared to the surface morphological properties in order to investigate the relation between the growth conditions and overall physical properties. The effects of composition, group V/III molar ratio and temperature on the InGaN material characteristics have been studied and the growth of high quality indium-rich InGaN epilayers are demonstrated.
14
Alevli, Mustafa. "Growth and Characterization of Indium Nitride Layers Grown by High-Pressure Chemical Vapor Deposition." Digital Archive @ GSU, 2008. http://digitalarchive.gsu.edu/phy_astr_diss/24.
Повний текст джерелаАнотація:
In this research the growth of InN epilayers by high-pressure chemical vapor deposition (HPCVD) and structural, optical properties of HPCVD grown InN layers has been studied. We demonstrated that the HPCVD approach suppresses the thermal decomposition of InN, and therefore extends the processing parameters towards the higher growth temperatures (up to 1100K for reactor pressures of 15 bar, molar ammonia and TMI ratios around 800, and a carrier gas flow of 12 slm). Structural and surface morphology studies of InN thin layers have been performed by X-ray diffraction, low energy electron diffraction (LEED), auger electron spectroscopy (AES), high-resolution electron energy loss spectroscopy (HREELS) and atomic force microscopy (AFM). Raman spectroscopy, infrared reflection, transmission, photoluminescence spectroscopy studies have been carried out to investigate the structural and optical properties of InN films grown on sapphire and GaN/sapphire templates. InN layers grown on a GaN (0002) epilayer exhibit single-phase InN (0002) X-ray diffraction peaks with a full width at half maximum (FWHM) around 200 arcsec. Auger electron spectroscopy confirmed the cleanliness of the surface, and low energy electron diffraction yielded a 1×1 hexagonal pattern indicating a well-ordered surface. The plasmon excitations are shifted to lower energies in HREEL spectra due to the higher carrier concentration at the surface than in the bulk, suggesting a surface electron accumulation. The surface roughness of samples grown on GaN templates is found to be smoother (roughness of 9 nm) compared to the samples grown on sapphire. We found that the deposition sometimes led to the growth of 3 dimensional hexagonal InN pyramids. Results obtained from Raman and IR reflectance measurements are used to estimate the free carrier concentrations, which were found in the range from mid 10^18 cm-3 to low 10^20 cm-3. The optical absorption edge energy calculated from the transmission spectra is 1.2 eV for samples of lower electron concentration. The Raman analysis revealed a high-quality crystalline layer with a FWHM for the E2(high) peak around 6.9 cm^-1. The results presented in our study suggest that the optimum molar ratio might be below 800, which is due to the efficient cracking of the ammonia precursor at the high reactor pressure and high growth temperature.
15
Hammersley, Simon. "Optical studies of group III-nitride semiconductors." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/optical-studies-of-group-iiinitride-semiconductors(01c6b437-d1f0-489e-91bf-0ebbf39119b6).html.
Повний текст джерелаАнотація:
In this thesis I will discuss the results of optical spectroscopy measurements in relation to the study of quantum well and multiple quantum well structures made up of group III-nitride semiconductors. This will include the results of photoluminesence(PL), reflectance, and time resolved photoluminesence spectroscopy experiments as well as the results of time correlated single photon counting (TCSPC) experiments. I have investigated the droop in efficiency observed in InGaN/GaN quantum wells as the current density or excitation power density is increased. I will show that at the onset of the efficiency droop a simultaneous reduction in the S-shape temperature dependence of the peak emission energy shift is observed. These results suggest that one of the mechanisms behind the efficiency droop is the saturation of localised states as the density of carriers is increased. I also discuss the carrier dynamics in non-polar GaN/AlGaN quantum wells intersected by basal plane stacking faults (BSF)s. In order to describe the form of the results of TCSPC results I put forward a model for the transfer of carriers from the quantum well into the regions of the quantum well intersected by BSFs. Finally I show the results of an investigation into the features observed in photoluminesence excitation measurements by N Hylton et al [1, 2] near the GaN band gap. These features are caused by a red shift in the peak emission energy using the results of PL measurements made as a function of excitation photon energy it is possible to resolve the lowest energy feature observed by Hylton et al into two features. Two possible mechanisms are then discussed for how the excitation of carriers at set energies above the GaN band gap results in a change to the peak energy of the quantum well emission.
16
Othick, Catherine Ann. "Optical characterisation of group III-nitride semiconductors." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/optical-characterisation-of-group-iii--nitride-semiconductors(715271fd-9e6c-4998-a9f9-24034cc43285).html.
Повний текст джерелаАнотація:
Research presented in this thesis focuses on the optical characterisation of InGaN/GaN quantum well (QW) and quantum dot (QD) structures and ScGaNepi layers, supported by microscopy results from the University of Cambridge. Reported in the first part of this thesis are the optical properties of sets of high In fraction (~25%) multiple QW structures designed to emit in the green part of the spectrum. Sets of InGaN/GaN QW structures were investigated which were grown using traditional methods but by varying QW growth temperature. These samples were found to have very broad photoluminescence linewidths and 1-10% room temperature IQE. Changes to the growth procedures had little effect on the improvement of the samples' luminescence properties. It was found that the first two wells of these samples were thicker and/or contained more indium than subsequent wells grown in the stack. The added thickness and/or indium content of these InGaN/GaN QWs resulted in lower energy emission than the rest of the QW stack, broadening the photoluminescence linewidth and decreasing the IQE. A modification of the growth procedures was developed to ensure that the individual QWs have as similar properties as possible so that the contribution to the PL linewidth due to well-to-well variations was significantly reduced. These modified procedures were used to produce new sets of InGaN/GaN 10 QW structures. These new structures showed a marked increase (~30%) in IQE and a significant decrease in PL linewidth. Furthermore, a set of 1, 3, 5 and 10 QW structures grown under modified growth procedures were investigated to determine the optimum number of QWs needed. It was found that 3 QWs provided a significant improvement to the IQE over the 1 QW samples; however, no additional improvements were realised by growing additional QWs. The second part of this thesis explores the use of macroscopic optical spectroscopy methods to study the properties of QDs. InGaN QDs are typically studied using spatially resolved techniques which allow for the study of individual dots in a structure. A sample which was known to contain InGaN QDs was investigated; however it was determined that macroscopic spectroscopic techniques were unable to determine the existence of QDs in the structure. Difficulties creating highly efficient green or near-UV light emitting InGaN semiconductors have lead to an interest in alternative material structures. One suggested alternative is to replace indium with the Group IIIB transition metal, scandium. The final part of this thesis explores a series of ~ 260 μm thick MBE grown ScGaN layers on 500 μm thick MOCVD-grown GaN templates. It was found that these materials, believed to contain up to 8% scandium, emit a broad spectrum violet luminescence. This broad luminescence spectrum resolves into multiple, narrower features with either increased substrate temperature during growth or by decreasing the scandium effusion cell temperature. The absorption spectrum, on the other hand, only shows evidence of GaN and samples grown at the highest substrate temperature revealed an exciton absorption feature near the band edge of GaN, a sign of increased crystal quality. These results have lead to questions as to whether the violet luminescence is due to the ternary alloy ScGaN or rather from shallow, radiative defects in the material.
17
Zado, Alexander [Verfasser]. "Metal-insulator-semiconductor structures and AlGaN/GaN hetero-junctions based on cubic group-III nitrides / Alexander Zado." Paderborn : Universitätsbibliothek, 2015. http://d-nb.info/1066728232/34.
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18
Fahle, Dirk [Verfasser]. "Investigation of HCl-assisted MOVPE of group III nitrides in a planetary hot-wall system / Dirk Fahle." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2014. http://d-nb.info/1058354388/34.
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19
Im, Jin Seo. "Spontaneous recombination in group-III nitride quantum wells." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963180800.
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20
Knelangen, Matthias. "Nucleation and growth of group III-nitride nanowires." Doctoral thesis, Humboldt-Universität zu Berlin, 2013. http://dx.doi.org/10.18452/16855.
Повний текст джерелаАнотація:
Diese Arbeit beschreibt das MBE-Wachstum und die Charakterisierung von Gruppe-III-Nitrid-Nanostrukturen. Die Arbeit beginnt mit dem katalysatorfreien Wachstum von GaN-Nanowires (NW) auf Si(111) mittels MBE. Es wird gezeigt, dass GaN NW als sph\"arische Inseln nukleieren und im weiteren Wachstum in eine NW-Geometrie übergehen. Die amorphe Zwischenschicht führt zum Verlust der epitaktischen Ausrichtung und somit zu gekippten Säulen und Koaleszenz. Diese Koaleszenz führt zur Enstehung von Versetzungen und Stapelfehlern in den Nanosäulen, welche einen starken Einfluss auf die optischen Eigenschaften haben: Während Versetzungen die Säulen optisch passivieren, haben Stapelfehler charakteristische Emissionen. Durch Kombination von Elektronenmikroskopie und Cathodolumineszenz wird die charateristische Wellenlänge eines Stapelfehlers gemessen. Epitaktisches Wachstum von GaN auf Si(111) kann durch die Verwendung einer AlN-Pufferschicht erreicht werden. Die Nukleation von GaN auf AlN/Si geschieht als linsenförmige Inseln. Im weiteren Verlauf des Wachstums erfolgen mehrere charakteristische Formübergänge, bei denen Facetten gebildet werden, um die Verspannung durch Gitterfehlanpassung elastisch zu relaxieren. Bei einer kritischen Inselgröße (und damit bei einem kritischen Spannungszustand) tritt eine platische Relaxation ein und es wird eine Versetzung an der AlN/GaN-Grenzfläche gebildet. Daraufhin tritt ein Übergang zur NW-Geometrie ein. Der dritte Teil dieser Arbeit beschreibt das Wachstum von (In,Ga)N/GaN NW Heterostrukturen. Mit MBE werden GaN NW mit zwei (In,Ga)N-Einschlüssen gewachsen. Die chemische Zusammensetzung wird mittels einer Kombination von hochauflösender Röntgenbeugung und einer Gitterverzerrungsanalyse von hochaufgelösten transmissionselektronenmikroskopischen Aufnahmen bestimmt. Die Strukturanalyse zeigt, dass die (In,Ga)N-Einschlüsse vollkommen in die GaN-Matrix eingebettet sind, und dass keine plastische Relaxation stattfindet.This work covers the MBE growth and characterization of group III-nitride nanostructures. The work begins with the catalyst-free growth of GaN nanowires (NWs) on Si(111) by plasma-assisted MBE. The importance of substrate preparation and the formation of an amorphous SiN interlayer are described. GaN NWs are shown to nucleate as spherical islands and to furhter undergo a shape transition towards the NW geometry. The amorphous interlayer leads to a loss in epitaxial alignment and thus to NW tilt and coalescence. Coalescence leads to the formation of dislocations and stacking faults (SFs) in the NWs which greatly affect their optical properties. Dislocations are shown to have a detrimental effect on the optical quality, whereas SFs are shown to have a characteristic emission wavelength. Epitaxial growth of GaN on Si(111) can be achieved by using an AlN buffer layer. The nucleation and growth GaN NWs on AlN-buffered Si(111) is shown to happen via the pseudomorphical nucleation of spherical islands. As these islands grow, they undergo several characteristical shape changes, with the formation of facets in order to elastically relieve the lattice-mismatch induced strain. At a critical island size (and thus strain level), plastic relaxation happens by the formation of a misfit dislocation at the AlN/GaN interface. A subsequent transition to the NW geometry is observed, driven by the anisotropy of surface energies. The third part of this work covers the growth of (In,Ga)N/GaN NW heterostructures. GaN NWs with two stacked (In,Ga)N insertions are grown by MBE. The chemical composition is assessed by combining synchrotron-based HRXRD and a geometrical phase analysis of HRTEM micrographs. The structural analysis reveals that the (In,Ga)N insertions are embedded in the GaN matrix and that no plastic relaxation happens. The In content is shown to vary within a single insertion: The top region is more In rich due to In segretation during growth.
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Chabrol, Gregoire Robert. "Optical investigations of group III-nitride quantum well structures." Thesis, University of Manchester, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492711.
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22
Hylton, Nicholas. "Optical spectroscopy of group III-nitride quantum well structures." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515223.
Повний текст джерелаАнотація:
Presented in this thesis is a detailed investigation of the optical properties of sets of InGaN/GaN and InGaN/AIGaN quantum well structures, supported by the results of microstructural experiments from the University of Cambridge. The effect of the depth of a single InGaN/GaN quantum well below the sample surface on its optical properties was investigated. Oscillations in the photoluminescence excitation spectra of the samples were observed at temperatures below 50 K and at photon energies above the GaN band gap. These features were attributed to the excitation of electrons at multiples of the LO-phonon energy above the GaN conduction band minimum. The rapid relaxation of the electrons and their capture into the quantum well led to a shift in the photoluminescence peak energy, and therefore the oscillations in the excitation spectra. The shifts in the photoluminescence spectra were attributed to a modification to the carrier distribution amongst localised states in the quantum well. A comparison of the optical properties of a set of semi-polar InGaN/GaN quantum well structures with those of nominally identical polar control samples was made. Evidence for a reduction in the electric field strength across the quantum wells was observed in the form of blue-shifts of the photoluminescence peak energy, increased rates of radiative recombination and sharpening of the quantum well excitation spectra, with respect to the controls. However, the reduction in the electric field strength across the wells does not result in an improvement in the room temperature internal quantum efficiency; an observation which was attributed to an increased density of non-radiative recombination centres due to an order of magnitude increase in the threading dislocation density in the semi-polar samples. The optical properties of a set of InGaN/AIGaN multiple quantum well samples with no capping layer, a GaN capping layer and a magnesium doped capping layer were also compared. It was found that the intensity of the quantum well luminescence in the capped samples was reduced at T = 6 K compared to that of the uncapped quantum wells, due to carriers generated in the cap layer not being captured into the wells. At room temperature the difference in quantum well luminescence intensity between the capped and uncapped samples increased due to the lower carrier density in the wells in the capped samples. In the case of the uncapped sample the higher carrier density resulted in the saturation of the impurity luminescence bands meaning that more carriers could contribute to the quantum well luminescence. However, in the capped samples the impurity luminescence was not saturated and so it is possible that carriers could be thermalised out of the wells and be captured at impurity sites, hence not contributing to the quantum well luminescence. Finally, the optical properties of InGaN/GaN multiple quantum well structures grown on 2 and 6 inch silicon substrates were studied. It was discovered that the reflectivity of silicon varies at low temperatures, which inevitably affects the outcome of measurements of internal quantum efficiency. After taking into account the effects of the changes to the reflectivity of the substrate, the room temperature photoluminescence internal quantum efficiencies of the samples were estimated to be 33 %,57 % (2 inch substrates) and 38 % (6 inch substrate).
23
Young, Craig Alexander. "Fabrication of photonic microstructures in group III nitride material." Thesis, University of Glasgow, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249984.
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24
Serban, Alexandra. "Magnetron Sputter Epitaxy of Group III-Nitride Semiconductor Nanorods." Licentiate thesis, Linköpings universitet, Tunnfilmsfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-141595.
Повний текст джерелаАнотація:
The III-nitride semiconductors family includes gallium nitride (GaN), aluminum nitride (AlN), indium nitride (InN), and related ternary and quaternary alloys. The research interest on this group of materials is sparked by the direct bandgaps, and excellent physical and chemical properties. Moreover, the ternary alloys (InGaN, InAlN and AlGaN) present the advantage of bandgap tuning, giving access to the whole visible spectrum, from near infrared into deep ultraviolet wavelengths. The intrinsic properties of III-nitride materials can be combined with characteristical features of nanodimension and geometry in nanorod structures. Moreover, nanorods offer the advantage of avoiding problems arising from the lack of native substrates, like lattice and thermal expansion, film – substrate mismatch. The growth and characterization of group III-nitride semiconductos nanorods, namely InAlN and GaN nanorods, is presented in this thesis. All the nanostructures were grown by employing direct-current reactive magnetron sputter epitaxy. InxAl1−xN self-assembled, core-shell nanorods on Si(111) substrates were demonstrated. A comprehensive study of temperature effect upon the morphology and composition of the nanorods was realized. The radial nanorod heterostructure consists of In-rich cores surrounded by Al-rich shells with different thicknesses. The spontaneous formation of core-shell nanorods is suggested to originate from phase separation due to spinodal decomposition. As the growth temperature increase, In desorption is favored, resulting in thicker Al-rich shells and larger nanorod diameters. Both self-assembled and selective-area grown GaN nanorods are presented. Self-assembled growth of GaN nanorods on cost-effective substrates offers a cheaper alternative and simplifies device processing. Successful growth of high- quality GaN (exhibiting strong bandedge emission and high crystalline quality) on conductive templates/substrates such as Si, SiC, TiN/Si, ZrB2/Si, ZrB2/SiC, Mo, and Ti is supported by the possibility to be used as electrodes when integrated in optoelectronic devices. The self-assembled growth leads to mainly random nucleation, resulting in nanorods with large varieties of diameters, heights and densities within a single growth run. This translates into non-uniform properties and complicates device processing. These problems can be circumvented by employing selective-area growth. Pre-patterned substrates by nano-sphere lithography resulted in GaN nanorods with controlled length, diameter, shape, and density. Well-faceted c-axis oriented GaN nanorods were grown directly onto the native SiOx layer inside nano-opening areas, exhibiting strong bandedge emission at room- temperature and single-mode lasing. Our studies on the growth mechanism revealed a different growth behavior when compared with selective-area grown GaN nanorods by MBE and MOCVD. The time-dependent growth series helped define a comprehensive growth mechanism from the initial thin wetting layer formed inside the openings, to the well-defined, uniform, hexagonal NRs resulted from the coalescence of multiple initial nuclei.
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Senawiratne, Jayantha. "Structural and Optical Characterization of Group III-Nitride Compound semiconductors." Digital Archive @ GSU, 2006. http://digitalarchive.gsu.edu/phy_astr_diss/7.
Повний текст джерелаАнотація:
The structural properties of the group III-nitrides including AlN, Ga1-xMnxN, GaN:Cu, and InN were investigated by Raman spectroscopy. Absorption and photoluminescence spectroscopy were utilized to study the optical properties in these materials. The analysis of physical vapor transport grown AlN single crystals showed that oxygen, carbon, silicon, and boron are the major impurities in the bulk AlN. The Raman analysis revealed high crystalline quality and well oriented AlN single crystals. The absorption coefficient of AlN single crystals were assessed in the spectral range from deep UV to the FIR. The absorption and photoluminescence analysis indicate that, in addition to oxygen, carbon, boron, and silicon, contribute to the optical properties of bulk AlN crystals. In situ Cu-doped GaN epilayers with Cu concentrations in the range of 2x10^16 cm-3 - 5x1017 cm-3, grown on sapphire substrate by metal organic chemical vapor deposition, were investigated by Raman and PL spectroscopy. The Raman study revealed high crystalline GaN:Cu layers with minimal damage to the hexagonal lattice structure due to the Cu incorporation. A strong Cu related emission band at 2.4 eV was assigned to Cu induced optical transitions between deep Cu states and shallow residual donor states. Compensation of Cu states by residual donors and poor activation probability of deep Cu states are responsible for semi-insulating electrical conductivity. Ferromagnetic Ga1-xMnxN epilayers, grown by MOCVD with Mn concentration from x = 0 to x = 1.5, were optically investigated by Raman, PL, and transmission spectroscopy. The Raman studies revealed Mn-related Raman peaks at 300 cm-1, 609 cm-1, and 669 cm-1. Mn-related absorption and emission bands in Ga1-xMnxN were observed at 1.5 eV and 3.0 eV, respectively. The structural properties of InN layers, grown by high pressure-CVD with different free carrier concentrations, were analyzed by Raman spectroscopy. The Raman results show that the InN layers have high crystalline quality. The free carriers in layers were calculated by using the Lindhard-Mermin dielectric function taking into account finite wave vectors for various scattering processes including forbidden Frohlich, deformational potential associated with allowed electro-optic, and charge density fluctuation, mechanisms. The free carrier concentrations in the layers are below 1x10^20 cm-3.
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Zhang, Hengfang. "Hot-wall MOCVD of N-polar group-III nitride materials." Licentiate thesis, Linköpings universitet, Halvledarmaterial, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-175502.
Повний текст джерелаАнотація:
Group III-Nitride semiconductors: indium nitride (InN), gallium nitride (GaN), aluminum nitride (AlN) and their alloys continue to attract significant scientific interest due to their unique properties and diverse applications in photonic and electronic applications. Group-III nitrides have direct bandgaps which cover the entire spectral range from the infrared (InN) to the ultraviolet (GaN) and to the deep ultraviolet (AlN). This makes III-nitride materials suitable for high-efficient and energy-saving optoelectronic devices, such as light-emitting diodes (LEDs) and laser diodes (LDs). The Nobel Prize in Physics 2014 was awarded for the invention of efficient GaN blue LEDs, which further accelerated the research in the field of group III-nitride materials. GaN and related alloys are also suitable for high-temperature, high-power and high-frequency electronic devices with performance that cannot be delivered by other semiconductor technologies such as silicon (Si) and gallium arsenide (GaAs). For example, GaN-based high electron mobility transistors (HEMTs) have been widely adopted for radio frequency (RF) communication and power amplifiers, high-voltage power switches in radars, satellites, and wireless base stations for 5G. Recently, nitrogen (N)-polar group-III nitrides have drawn much attention due to their advantages over their metal-polar counterparts in e.g. HEMTs. These include feasibility to fabricate ohmic contacts with low resistance, an enhanced carrier confinement with a natural back barrier, and improved device scalability. Despite intensive research, the growth of micrometer-thick high-quality N-polar GaN based materials remains challenging. One of the major problems to develop device-quality N-polar nitrides is the high surface roughness, which results from the formation of hexagonal hillocks or step-bunching. Another significant hurdle is the unintentional polarity inversion, which reduces the crystalline quality and prohibits device fabrication. This licentiate thesis focuses on the development of N-polar AlN and GaN heterostructures on SiC substrates for HEMT RF applications. The overall aim is to exploit the advantages of the hot-wall MOCVD concept to grow high-quality N-polar HEMT structures for higher operational frequencies and improved device performance. In order to achieve this goal, special effort is dedicated to understanding the effects of growth conditions and substrate orientation on the structural properties and polarity of AlN, GaN and AlGaN grown by hot-wall MOCVD. N-polar AlN nucleation layers (NLs) with layer by layer growth mode and step-flow growth mode can be achieved on on-axis and 4_ offaxis SiC (000¯1), respectively, by carefully controlling V/III ratio and growth temperature. Utilizing scanning transmission electron microscopy (STEM) we have established a comprehensive picture of the atomic arrangements, local polarity and polarity evolution in AlN, GaN/AlN and AlGaN/GaN/AlN in the cases of low-temperature and high-temperature AlN NLs both for on-axis and off-axis substrates. We have shown that typically employed methods for polarity determination using potassium hydroxide wet etching could not provide conclusive results in the case of mixed-polar AlN as Al-polar domains may be easily over-etched and remain undetected. Atomic scale electron microscopy is therefore needed to accurately determine the polarity. We further have developed growth strategy and have optimized the epitaxial process for N-polar GaN, and have demonstrated high quality N-polar AlGaN/GaN/AlN heterostructures.Additional funding agencies: Chalmers University of technology; ABB; Ericsson; Epiluvac; FMV; Gotmic; Saab; SweGaN; UMS; Swedish Foundation for Strategic Research under Grants No. FL12-0181, No. RIF14-055, and No. EM16-0024; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University, Faculty Grant SFO Mat LiU No.2009- 00971.
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Adelmann, Hans Christoph. "Growth and strain relaxation mechanisms of group III nitride heterostructures." Université Joseph Fourier (Grenoble), 2002. http://www.theses.fr/2002GRE10039.
Повний текст джерелаАнотація:
Ce travail a porté sur les mécanismes de croissance épitaxiale et de relaxation de contrainte d'hétérostructures de nitrures d'éléments III, GaN et AIN, en épitaxie par jets moléculaires assistée par plasma d'azote. Nous avons étudié les structures de la surface (0001) de GaN et d'AIN en conditions d'excès de métal. Nous avons montré que la quantité de Ga absorbée sur GaN peur être évaluée par RHEED. Cette méthode a été appliquée à l'absorption de Ga et à la croissance de GaN en conditions riche Ga. Dans les deux cas, les résultats ont permis de tracer un diagramme qui décrit la quantité de Ga présente sur GaN en fonction du flux de Ga et de la température de croissance. Les morphologies de surface obtenues après la croissance de GaN dans les différentes parties du diagramme sont discutées. Nous avons ensuite abordé la relaxation des contraintes d'hétérostructures GaN/AIN. En conditions d'excès d'azote, la relaxation se produit de façon élastique, soit par la formation d'îlots plats à basse température, soit par la formation d'îlots pyramidaux selon le mode Stranski-Krastanow à haute température. En conditions d'excès de métal, la croissance est bidimensionnelle et la relaxation se produit par introduction de dislocations. Nous avons démontré que l'épaisseur critique de cette relaxation plastique dépend fortement des conditions de croissance. L'étude de la nucléation d'îlots de GaN sur AIN en mode Stranski-Krastanowa permis de contrôler leur taille et leur densité. Ces deux paramètres peuvent être variés de façon indépendante dans une large gamme de valeurs. Nous avons trouvé que l'optimisation de la distribution de taille des îlots est compliquée par une distribution bimodale à haute température. Finalement, nous avons étudié l'adsorption de Ga sur les surfaces (0001) d'AIN et d'AlGaN. Ceci a permis de démontrer la faisabilité d'épitaxie en flux alternés de GaN sur AIN et AlGaN.
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Bao, An. "Investigation on the properties of nanowire structures and hillocks of Group-III nitride materials." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/276187.
Повний текст джерелаАнотація:
Group-III nitride materials are increasingly important, because of their semiconducting properties and bandgaps tuneable across a wide range from the infrared to ultraviolet. They are of particular interest for optoelectronic and power electronic applications. The studies on nitride materials are comprehensive, and one way to categorise them is based on the scale of the material, namely: (a) 3D bulk materials, for example the development of 3D bulk nitride substrate; (b) epitaxial layers, for example GaN/InGaN 2D quantum well based light emitting diodes (LEDs); (c) 1D nitride nanowires and (d) 0D quantum dots, for example InGaN quantum dot based single photon sources. This thesis uses a multimicroscopy concept to investigate various group-III nitride nanowires and hillocks. Multiple different microscopy techniques were applied to the same specific nanostructure or defect. This allows the properties of the materials of interest to be linked directly to the nanostructures or defects, providing a more complete picture of the samples that have been studied. The multiple microscopy techniques used to conduct the work in this thesis include (scanning) transmission electron microscopy ((S)TEM), cathodoluminescence (CL), focused ion beam (FIB) and atomic force microscopy (AFM). Specifically, AFM was used to characterise the morphology of the sample on a sub-nanometer scale. The crystalline structures were characterised using (S)TEM, and the in-situ energy dispersive X-ray spectroscopy (EDS) was used to conduct compositional analysis of the selected sites. CL was used to reveal the optoelectronic properties by analysing the emission wavelengths of the materials, excited by the electron beam. FIB was the technique used to prepare site-specific samples to be measured in (S)TEM. A detailed explanation of these characterisation techniques was also included. In the context of the studies on nitride materials, nitride nanowires and their heterostructures are a particular research focus. They combine the unique properties of III-nitride materials together with the advantages induced by the nanowire geometry. This thesis explores three different nanowire systems: a GaN nanowire structure incorporating a GaN/Sc$_x$Ga$_{1-x}$N axial heterostructure grown by molecular beam epitaxy (MBE); GaN/InGaN core-shell nanowires fabricated by a hybrid approach combining metalorganic vapour phase epitaxy (MOVPE) and dry etching techniques; and AlGaN nanowires on free standing AlGaN substrates fabricated by MBE and inductively coupled plasma (ICP) etching. The optoelectronic properties, compositions and structures of these nanowires were studied in detail. Moreover, a comprehensive review on the properties, growth methods and applications of group-III nitride nanowires is also included in this thesis. Apart from nanowires, a lot of effort has been focusing on the improvement of the quality of epitaxial layers of GaN and its alloys, and they currently have an even wider perspective than nitride nanowires. The understanding of defects within the epitaxial layers is crucial in order to mitigate the their adverse effects, leading to the increased emphasis on defect analysis. Hillocks are a type of defects found on GaN epilayers, which are less well studied than other defects such as dislocations and stacking faults. As a consequence, the formation mechanisms of hillocks remain controversial. In this context, after a review on the past studies on GaN hillocks, this thesis also investigates two types of hillocks, i.e. hillocks on GaN p-i-n diodes and hillocks on GaN grown on patterned sapphire substrates (PSS). Their nanoscale structures, properties and formation mechanisms are studied.
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Hoffman, Timothy B. "Optimization and characterization of bulk hexagonal boron nitride single crystals grown by the nickel-chromium flux method." Diss., Kansas State University, 2016. http://hdl.handle.net/2097/32797.
Повний текст джерелаАнотація:
Doctor of PhilosophyDepartment of Chemical Engineering
James H. Edgar
Hexagonal boron nitride (hBN) is a wide bandgap III-V semiconductor that has seen new interest due to the development of other III-V LED devices and the advent of graphene and other 2-D materials. For device applications, high quality, low defect density materials are needed. Several applications for hBN crystals are being investigated, including as a neutron detector and interference-less infrared-absorbing material. Isotopically enriched crystals were utilized for enhanced propagation of phonon modes. These applications exploit the unique physical, electronic and nanophotonics applications for bulk hBN crystals. In this study, bulk hBN crystals were grown by the flux method using a molten Ni-Cr solvent at high temperatures (1500°C) and atmospheric pressures. The effects of growth parameters, source materials, and gas environment on the crystals size, morphology and purity were established and controlled, and the reliability of the process was greatly improved. Single-crystal domains exceeding 1mm in width and 200μm in thickness were produced and transferred to handle substrates for analysis. Grain size dependence with respect to dwell temperature, cooling rate and cooling temperature were analyzed and modeled using response surface morphology. Most significantly, crystal grain width was predicted to increase linearly with dwell temperature, with single-crystal domains exceeding 2mm in at 1700°C. Isotopically enriched ¹⁰B and ¹¹B hBN crystal were produced using a Ni-Cr-B flux method, and their properties investigated. ¹⁰B concentration was evaluated using SIMS and correlated to the shift in the Raman peak of the E[subscript 2g] mode. Crystals with enrichment of 99% ¹⁰B and >99% ¹¹B were achieved, with corresponding Raman shift peaks at 1392.0 cm⁻¹ and 1356.6 cm⁻¹, respectively. Peak FWHM also decreased as isotopic enrichment approached 100%, with widths as low as 3.5 cm⁻¹ achieved, compared to 8.0 cm⁻¹ for natural abundance samples. Defect selective etching was performed using a molten NaOH-KOH etchant at 425°C-525°C, to quantify the quality of the crystals. Three etch pit shapes were identified and etch pit width was investigated as a function of temperature. Etch pit density and etch pit activation energy was estimated at 5×10⁷ cm⁻² and 60 kJ/mol, respectively. Screw and mixed-type dislocations were identified using diffraction-contrast TEM imaging.
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Hölzel, Sara Sibylle [Verfasser]. "Group III-Nitride Nanowires as Multifunctional Optical Biosensors / Sara Sibylle Hölzel." Gießen : Universitätsbibliothek, 2018. http://d-nb.info/1173615059/34.
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Hölzel, Sara [Verfasser]. "Group III-Nitride Nanowires as Multifunctional Optical Biosensors / Sara Sibylle Hölzel." Gießen : Universitätsbibliothek, 2018. http://d-nb.info/1173615059/34.
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Waltereit, Patrick. "(Al, Ga, In)N heterostructures grown along polar and non-polar directions by plasma-assisted molecular beam epitaxy." Doctoral thesis, [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963284975.
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Miskys, Claudio Ronald. "New substrates for epitaxy of group III nitride semiconductors : challenges and potential /." München : Walter-Schottky-Institut, Technische Universität München, 2007. http://opac.nebis.ch/cgi-bin/showAbstract.pl?u20=9783932749841.
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Miskys, Claudio Ronald. "New substrates for epitaxy of group III nitride semiconductors challenges and potential /." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=97306854X.
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Deppe, Michael [Verfasser]. "Germanium doping of aluminum-containing cubic group III-nitride heterostructures / Michael Deppe." Paderborn : Universitätsbibliothek, 2020. http://d-nb.info/1217711090/34.
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Davis, Carl Steven. "Studies of group III-nitride semiconductor compounds grown by molecular beam epitaxy." Thesis, University of Nottingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423657.
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Mihopoulos, Theodoros 1969. "Reaction and transport processes in OMCVD : selective and group III-nitride growth." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9655.
Повний текст джерелаАнотація:
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1999.Includes bibliographical references.
Researchers have continued to explore light sources that are brighter, cheaper, more reliable, and emit light closer to natural sunlight than conventional incandescent and fluorescent lighting. The most recent advance in this direction is the fabrication of light emitting diodes (LEDs), and laser diodes that can emit in the short wavelength region of the visible spectrum (from green to violet). By using organometallic chemical vapor deposition (OMCVD) to fabricate thin films of the group III nitride materials (GaN, AIN, and InN), LEDs with lifetimes over 10,000 hours are now commercially available while rapid progress is being made towards a laser diode structure with a similar lifetime. These devices, coupled with the existing red, yellow, orange, and amber LEDs (based on AIInGaP, also grown by OMCVD) whose light-emission efficiency is already superior to incandescent lamps can lead to full color solid-sate light sources. OMCVD of AlGaInN involves complex chemistry and flow phenomena, which determine the quality of the deposited layers. Incorporation of significant concentrations of Al and In have proven difficult to achieve. The understanding of the dominant reaction pathways and their interaction with transport phenomena has been insufficient for design and optimization of nitride deposition processes. This thesis describes coupled finite element simulations of fluid flow, heat and mass transfer with emphasis on constructing kinetic mechanisms that incorporate all the chemistry information known by experimental studies and quantum chemistry calculations. A kinetic mechanism for GaN deposition is proposed. The model involves fast reaction between trimethylgallium and NH3 to form a Lewis type acid-base adduct which can dissociate or decompose at higher temperatures. The decomposition fragments can subsequently react to form dimer or trimer complexes in the gas phase containing multiple gallium-nitrogen bonds. Reaction rate parameters are obtained from quantum chemistry calculations in the literature and analysis of experimental data. The reaction mechanism is shown to be consistent with individual experimental observations, flow-tube decomposition studies, and growth rate temperature and pressure dependence in a horizontal OMCVD reactor as well as growth rate data in a close-spaced OMCVD reactor. The growth rate appears to be limited by GaN formation at low temperatures, mass transport at intermediate temperatures and GaN decomposition at temperatures higher than 1000°C. Dimer and trimer formation provide additional pathways of Ga supply to the surface at low temperatures and high pressures. In order to simulate nitride growth in a new OMCVD reactor with close-spaced-injector, a hierarchical simulation approach of fluid flow and mass transfer in such reactors was initially performed. Three-dimensional calculations establish that there is complete mixing in the gas phase, while the individual gas injectors dissipate within 5-8 mm from the reactor inlet under typical operating conditions. Two-dimensional parametric studies of growth rate and uniformity dependence on operating conditions and geometric factors were used to gain insight into the chamber performance. Regions of stagnation and rotating disk flows were delineated as a function of operating parameters. In the case of rotating disk flow, growth uniformity increases with pressure, contrary to the classical vertical rotating disk reactor response. A mechanism for AIN growth is also described. Formation of dimers and trimers in the gasphase is identified as the major pathway for decreased growth efficiency with decreasing pressure. An additional pathway involving nucleation and growth of oligomers from dimers and trimers, and ultimately particle formation, is consistent with decreased growth efficiency with increasing temperature. The kinetic model is consistent with experimental observations of temperature and pressure dependence of AIN growth rate in a horizontal hot-wall reactor and growth rate data for AlGaN in a close-spaced reactor. In agreement with experimental observations, the simulations predict AIN deposition in a close-spaced reactor under conditions that prohibit AIN growth in a horizontal reactor. Thin films of InxGalxN are used as the active region in the III-N devices. Thus, controlling the indium composition in a reproducible manner is imperative for III-N device fabrication. The solid indium mole fraction in InGaN is reported to independently depend on temperature, relative indium amount at the inlet, film growth rate, and carrier gas used. A simple trapping mechanism is proposed for InN growth in InGaN ternary alloys. In agreement with multiple experimental observations, the indium content appears to be controlled by competition between desorption kinetics and incorporation, the latter being determined by the GaN growth rate since InN is not stable under typical growth conditions. The effect of H2 carrier gas on indium mole fraction is also discussed. For laser diode fabrication in the III-Nitride system, selective area growth is used to deposit buffer layers with fewer dislocations. In addition to its recent use in the nitride system, selective area epitaxy has been pursued in OMCVD of III-V compound semiconductors in general. Quantitative understanding of selective epitaxy, in particular compositional variations arising in selective growth of ternary alloys such as InGaAs and InGaP that are currently not understood, is needed to realize advanced optoelectronic devices. A hierarchical modeling approach of selective area epitaxy is undertaken to identify the origins of growth rate enhancement and indium composition enrichment in the case of ternary InGa(As/P) growth. Simulations using the stagnant layer approach reveal that surface reaction rate differences give rise to the compositional modulation. A realistic fluid flow description in a vertical axisymmetric reactor is coupled with a simple kinetic mechanism for InGaAs/P deposition. Differences in homogeneous decomposition kinetics of In and Ga precursors give rise to different "effective" surface reaction rates that lead to the observed In-enrichment. The proposed model is in agreement with reports on the dependence of In-enrichment on operating parameters. Simulations show that, while the alloy deposition is limited by mass transport, differences in reaction rates are responsible for the composition variations in selective growth. Thus, the usefulness of reaction-transport models in elucidating the relative roles of different deposition pathways and gaining insight to the deposition process is demonstrated. Growth rate enhancement and In-enrichment model predictions are in excellent agreement with experimental data on lateral and axial dependence obtained in a horizontal reactor with a large masked area.
by Theodoros Mihopoulos.
Ph.D.
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Darakchieva, Vanya. "Strain-related structural and vibrational properties of group-III nitride layers and superlattices /." Linköping : Univ, 2004. http://www.bibl.liu.se/liupubl/disp/disp2004/tek891s.pdf.
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Wallys, Jens Matthias Emil [Verfasser]. "Characterization of group IIInitride nanowires for bioelectrochemical sensors / Jens Matthias Emil Wallys." Gießen : Universitätsbibliothek, 2014. http://d-nb.info/1068534796/34.
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Hille, Pascal [Verfasser]. "Advanced group III-nitride nanowire heterostructures - self-assembly and position-controlled growth / Pascal Hille." Gießen : Universitätsbibliothek, 2017. http://d-nb.info/1132510511/34.
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Суховій, Ніна Олегівна. "Нанотемплети для гетероструктур нітридів III групи". Doctoral thesis, Київ, 2018. https://ela.kpi.ua/handle/123456789/24998.
Повний текст джерелаАнотація:
Дисертаційна робота присвячена комплексному дослідженню застосувань і розробок технологічних рішень щодо формування нанотемплетів для гетероструктур ІІІ-нітридів, в тому числі з неполярною кристалографічною орієнтацією, щодо забезпечення малодефектності і можливості одержання наноструктур (наностержнів, квантових точок, тощо) для їх практичної реалізації в оптоелектронних інтегральних схемах.
В ході досліджень для нітрид галію неполярної (112̅0) орієнтації з використанням нанотемплетів анодованого оксиду алюмінію на Si(100) одержано щільність дислокацій 3х106 см-2, що дає змогу формувати InGaN/GaN КЯ і КТ з підвищеним вмістом індію.
Згідно запропонованої спрощеної математичної моделі, встановлено, що може бути забезпечена низька щільність дислокацій при будь-якій глибині пір при радіусах пір < 10 нм, одержання яких за допомогою нанотемплетів анодного оксиду алюмінію дуже проблематично. Проте, для MOCVD епітаксії були експериментально визначені термодинамічні параметри (температура, тиск) та прекурсори, при яких на поверхні сапфіру утворюються нанопори з радіусом <10нм. На одержаних темплетах нанотекстурованого сапфіру була показана можливість в одному технологічному циклі вирощувати гетероепітаксійні шари ІІІ-нітридів з низькою щільністю дислокацій (~ 5 х 106 см-2).
Ключові слова: нанотемплети, гетероструктури, нітриди ІІІ групи, малодефектність, анодований оксид алюмінію.
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Atalay, Ramazan. "Optical and Structural Properties of Indium Nitride Epilayers Grown by High-Pressure Chemical Vapor Deposition and Vibrational Studies of ZGP Single Crystal." Digital Archive @ GSU, 2012. http://digitalarchive.gsu.edu/phy_astr_diss/60.
Повний текст джерелаАнотація:
The objective of this dissertation is to shed light on the physical properties of InN epilayers grown by High-Pressure Chemical Vapor Deposition (HPCVD) for optical device applications. Physical properties of HPCVD grown InN layers were investigated by X-ray diffraction, Raman scattering, infrared reflection spectroscopies, and atomic force microscopy. The dependencies of physical properties as well as surface morphologies of InN layers grown either directly on sapphire substrates or on GaN/sapphire templates on varied growth conditions were studied. The effect of crucial growth parameters such as growth pressure, V/III molar ratio, precursor pulse separation, substrate material, and mass transport along the flow direction on the optical and structural properties, as well as on the surface morphologies were investigated separately.
At present, growth of high-quality InN material by conventional growth techniques is limited due to low dissociation temperature of InN (~600 ºC) and large difference in the partial pressures of TMI and NH3 precursors. In this research, HPCVD technique, in which ambient nitrogen is injected into reaction zone at super-atmospheric growth pressures, was utilized to suppress surface dissociation of InN at high temperatures.
At high pressures, long-range and short-range orderings indicate that c-lattice constant is shorter and E2(high) mode frequency is higher than those obtained from low-pressure growth techniques, revealing that InN structure compressed either due to a hydrostatic pressure during the growth or thermal contraction during the annealing. Although the influence of varied growth parameters usually exhibit consistent correlation between long-range and short-range crystalline orderings, inconsistent correlation of these indicate inclination of InN anisotropy.
InN layers, grown directly on α-sapphire substrates, exhibit InN (1 0 1) Bragg reflex. This might be due to a high c/a ratio of sapphire-grown InN epilayers compared to that of GaN/sapphire-grown InN epilayers. Optical analysis indicates that free carrier concentration, ne, in the range of 1–50 × 1018 cm–3 exhibits consistent tendency with longitudinal-optic phonon. However, for high ne values, electrostatic forces dominate over inter-atomic forces, and consistent tendency between ne and LO phonon disappears.
Structural results reveal that growth temperature increases ~6.6 ºC/bar and V/III ratio affects indium migration and/or evaporation. The growth temperature and V/III ratio of InN thin films are optimized at ~850 ºC and 2400 molar ratio, respectively. Although high in-plane strain and c/a ratio values are obtained for sapphire-grown epilayers, FWHM values of long-range and short-range orderings and free carrier concentration value are still lower than those of GaN/sapphire-grown epilayers.
Finally, vibrational and optical properties of chalcopyrite ZGP crystal on the (001), (110), and (10) crystalline planes were investigated by Raman scattering and infrared (IR) reflection spectroscopies. Raman scattering exhibits a nonlinear polarizability on the c-plane, and a linear polarizability on the a- and b-planes of ZGP crystal. Also, birefringence of ZGP crystal was calculated from the hydrostatic pressure difference between (110) and (10) crystalline planes for mid-frequency B2(LO) mode.
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Johnson, Michael Christopher. "In-situ and post-growth investigation of low temperature Group III-nitride thin films deposited via MOCVD /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/9925.
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Butler, Sween J. "Nonlinear Light Generation from Optical Cavities and Antennae." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc984232/.
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Semiconductor based micro- and nano-structures grown in a systematic and controlled way using selective area growth are emerging as a promising route toward devices for integrated optical circuitry in optoelectronics and photonics field. This dissertation focuses on the experimental investigation of the nonlinear optical effects in selectively grown gallium nitride micro-pyramids that act as optical cavities, zinc oxide submicron rods and indium gallium nitride multiple quantum well core shell submicron tubes on the apex of GaN micro pyramids that act as optical antennae. Localized spatial excitation of these low dimensional semiconductor structures was optimized for nonlinear optical light (NLO) generation due to second harmonic generation (SHG) and multi-photon luminescence (MPL). The evolution of both processes are mapped along the symmetric axis of the individual structures for multiple fundamental input frequencies of light. Effects such as cavity formation of generated light, electron-hole plasma generation and coherent emission are observed. The efficiency and tunability of the frequency conversion that can be achieved in the individual structures of various geometries are estimated. By controlling the local excitation cross-section within the structures along with modulation of optical excitation intensity, the nonlinear optical process generated in these structures can be manipulated to generate coherent light in the UV-Blue region via SHG process or green emission via MPL process. The results show that these unique structures hold the potential to convert red input pulsed light into blue output pulsed light which is highly directional.
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Knelangen, Matthias [Verfasser], Henning [Akademischer Betreuer] Riechert, Andreas [Akademischer Betreuer] Waag, and Ted W. [Akademischer Betreuer] Masselink. "Nucleation and growth of group III-nitride nanowires / Matthias Knelangen. Gutachter: Henning Riechert ; Andreas Waag ; Ted W. Masselink." Berlin : Humboldt Universität zu Berlin, 2013. http://d-nb.info/1044956275/34.
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Lambert, Damien Jean Henri. "Growth and characterization of group III-nitride power transistors, power rectifiers and solar-blind detectors by metalorganic chemical vapor deposition /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004311.
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Wille, Ada Verfasser], Andrei [Akademischer Betreuer] [Vescan, and Rainer [Akademischer Betreuer] Waser. "Investigation of AlN/GaN superlattices and their application to group III nitride devices / Ada Wille ; Andrei Vescan, Rainer Waser." Aachen : Universitätsbibliothek der RWTH Aachen, 2017. http://d-nb.info/1130872599/34.
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Reuters, Benjamin Verfasser], Andrei [Akademischer Betreuer] [Vescan, and Ferdinand [Akademischer Betreuer] Scholz. "Polarization-optimized heterostructures with quaternary AlInGaN layers for novel group III nitride devices / Benjamin Reuters ; Andrei Vescan, Ferdinand Scholz." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1129875652/34.
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Wille, Ada [Verfasser], Andrei [Akademischer Betreuer] Vescan, and Rainer [Akademischer Betreuer] Waser. "Investigation of AlN/GaN superlattices and their application to group III nitride devices / Ada Wille ; Andrei Vescan, Rainer Waser." Aachen : Universitätsbibliothek der RWTH Aachen, 2017. http://d-nb.info/1130872599/34.
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Reuters, Benjamin [Verfasser], Andrei [Akademischer Betreuer] Vescan, and Ferdinand [Akademischer Betreuer] Scholz. "Polarization-optimized heterostructures with quaternary AlInGaN layers for novel group III nitride devices / Benjamin Reuters ; Andrei Vescan, Ferdinand Scholz." Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1129875652/34.
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