| 1. |
- Abdelgadir, Moawia, 1965-
(författare)
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Clinical and Biochemical Features of Adult Diabetes Mellitus in Sudan
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The high prevalence of diabetes mellitus among the Sudanese population is linked to obesity, poor glycaemic control and a high rate of complications. This study investigated 1/ Leptin hormone and its correlations with different biochemical characteristics in Sudanese diabetic subjects, 2/ The impact of glycaemic control on pregnancy outcome in pregnancies with diabetes, 3/ The glycaemic response to Sudanese traditional carbohydrate foods, 4/ The influence of glucose self-monitoring on the glycaemic control among this population, 5/ The health related quality of life in Sudanese subjects with diabetes-related lower limb amputation. Leptin was significantly lower in diabetic subjects compared with controls of same BMI in both females (P =0.0001) and males (P =0.019). In diabetic subjects, serum leptin correlated positively with the homeostatic assessment (HOMA) of both beta-cell function (P =0.018) and insulin resistance (P =.038). In controls, leptin correlated only with insulin resistance. Pregnancy complications were higher among diabetic compared with control women (P<0.0001) and varied with the type of diabetes. Infants of diabetic mothers had a higher incidence of neonatal complications than those of non-diabetic women (P<0.0001). In six Sudanese traditional carbohydrate meals over all differences in incremental AUCs were significant for both plasma glucose (P = 0.0092) and insulin (P = 0.0001). Millet porridge and wheat pancakes displayed significantly lower post-prandial glucose and insulin responses, whereas maize porridge induced a higher post-prandial glucose and insulin response. In type 2 diabetic subjects SMBG or SMUG was not related to glycaemic control. In type 1 diabetic subjects, SMBG was significantly associated with better glycaemic control, as assessed by HbA1c (P=0.02) and blood glucose at clinic visits (P=<0.0001), similar associations were found for SMUG respectively. Neither glycaemic control nor glucose self-monitoring was associated with education level. Diabetic subjects with LLA had significantly poorer HRQL compared to a reference diabetic group (P=<0.0001). Duration of diabetes and amputation had negative impact on HRQL in subjects with LLA (P=<0.0001) respectively. Diabetic subjects with LLA had decreased sense of coherence and high presence of symptoms. Improving health services at the primary level is important to reduce the complications and burden of disease in the Sudanese population.
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| 2. |
- Ahlin, Gustav, 1977-
(författare)
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In vitro and in silico prediction of drug-drug interactions with transport proteins
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Drug transport across cells and cell membranes in the human body is crucial for the pharmacological effect of drugs. Active transport governed by transport proteins plays an important role in this process. A vast number of transport proteins with a wide tissue distribution have been identified during the last 15 years. Several important examples of their role in drug disposition and drug-drug interactions have been described to date. Investigation of drug-drug interactions at the transport protein level are therefore of increasing interest to the academic, industrial and regulatory research communities. The gene expression of transport proteins involved in drug transport was investigated in the jejunum, liver, kidney and colon to better understand their influence on the ADMET properties of drugs. In addition, the gene and protein expression of transport proteins in cell lines, widely used for predictions of drug transport and metabolism, was examined. The substrate and inhibitor heterogeneity of many transport proteins makes it difficult to foresee whether the transport proteins will cause drug-drug interactions. Therefore, in vitro assays for OCT1 and OATP1B1, among the highest expressed transport proteins in human liver, were developed to allow investigation of the inhibitory patterns of these proteins. These assays were used to investigate two data sets, consisting of 191 and 135 registered drugs and drug-like molecules for the inhibition of OCT1 and OATP1B1, respectively. Numerous new inhibitors of the transport proteins were identified in the data sets and the properties governing inhibition were determined. Further, antidepressant drugs and statins displayed strong inhibition of OCT1 and OATP1B1, respectively. The inhibition data was used to develop predictive in silico models for each of the two transport proteins. The highly polymorphic nature of some transport proteins has been shown to affect drug response and may lead to an increased risk of drug-drug interactions, and therefore, the OCT1 in vitro assay was used to study the effect of common genetic variants of OCT1 on drug inhibition and drug-drug interactions. The results indicated that OCT1 variants with reduced function were more susceptible to inhibition. Further, a drug-drug interaction of potential clinical significance in the genetic OCT1 variant M420del was proposed. In summary, gene expression of transport proteins was investigated in human tissues and cell lines. In vitro assays for two of the highest expressed liver transport proteins were used to identify previously unknown SLC transport protein inhibitors and to develop predictive in silico models, which may detect previously known drug-drug interactions and enable new ones to be identified at the transport protein level. In addition, the effect of genetic variation on inhibition of the OCT1 was investigated.
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| 3. |
- Amloy, Supaluck, 1980-
(författare)
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Polarization-resolved photoluminescence spectroscopy of III-nitride quantum dots
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis, results from studies on (In)GaN quantum dots (QDs) are presented, including investigations of the structural, optical and electronic properties. The experimental studies were performed on GaN and InGaN QDs grown by molecular beam epitaxy, taking advantage of the Stranki-Krastanov growth mode for the GaN QD samples and the composition segregation for the InGaN QD samples.Optical spectroscopy of the (In)GaN QDs was performed with a combination of different experimental techniques, e.g. stationary microphotoluminescence (μPL) and timeresolved μPL. The μPL spectroscopy is suitable for studies of single QDs due to the wellfocused excitation laser spot, and it typically does not require any special sample preparation. The powerful combination of power and polarization dependences was used to distinguish the exciton and the biexciton emissions from other emission lines in the recorded spectra.The QDs could be observed with random in-plane anisotropy, as determined by the strong linear polarization for single QDs but with different angular orientation from dot to dot. Additionally, these experimental results are in good agreement with the computational results revealing a similar degree of polarization for the exciton and the biexciton emissions. Further, the theory predicts that the discrepancy of the polarization degree is larger between the positive and negative trions in comparison with the exciton and the biexciton. Based on this result, polarization resolved spectroscopy is proposed as a simple tool for the identification of trions and their charge states.The fine-structure splitting (FSS) and the biexciton binding energy (Ebxx) are essential QD parameters of relevance for the possible generation of quantum entangled photon pairs in a cascade recombination of the biexciton. In general, the Coulomb interaction between the negatively charged electron and the positively charged hole lifts the fourfold degeneracy of the electron and hole pair ground state, forming a set of zero-dimensional exciton states of unequal energies. This Coulomb-induced splitting, referred to as the FSS, results in an electronic fine structure, which is strongly dependent on the symmetry of the exciton wave function. The FSS was in this work resolved and investigated for excitons in InGaN QDs, using polarization-sensitive μPL spectroscopy employed on the cleaved-edge of the samples. As expected, the FSS is found to exhibit identical magnitudes, but with reversed sign for the exciton and the biexciton. For quantum information applications, a vanishing FSS is required, since otherwise the emissions of the polarization-entangled photon pairs in the cascade biexciton recombination will be prohibited.The biexcitons are found to exhibit both positive and negative binding energies for the investigated QDs. Since a negative binding energy indicates a repulsive Coulomb interaction, such biexcitons (or exciton complexes) cannot exist in structures of higher dimensionality. On the other hand, a biexciton with a negative binding energy can be found in QDs, since the exciton complexes still remain bound due to their three dimensional confinement. Moreover, the biexciton binding energy depends on the dot size, which implies that a careful size control of dots could enable manipulation of the biexciton binding energy. A large Ebxx value enables better and cheaper spectral filtering, in order to purify the single photon emission, while a proposed time reordering scheme relies on zero Ebxx for the generation of entangled photons.The dynamics of the exciton and the biexciton emissions from InGaN QD were measured by means of time-resolved μPL. The lifetimes of the exciton related emissions are demonstrated to depend on the dot size. Both the exciton and the biexciton emissions reveal mono-exponential decays, with a biexciton lifetime, which is about two times shorter than the exciton lifetime. This implies that the QD is small, with a size comparable to the exciton Bohr radius. The photon generation rates can be manipulated by controlling the QDs size, which in turn can be utilized for generation of single- and entangled-photons on demand, with a potential for applications in e.g. quantum information.The polarization of the emitted single photons can be manipulated by using a polarizer, but to the prize of photon loss and reduced emission intensity. Alternative methods to control the polarization of the emission light are a manipulation of the dot symmetry statically by its shape or dynamically by an externally applied electric field. Predictions based on performed calculations show that in materials with a small spin-orbit split-off energy (ΔSO), like the III-nitride materials, the polarization degree of the emission is more sensitive to dot asymmetry than in materials with a large value for ΔSO, e.g. the III-arsenide materials. Moreover, for an electric field applied in the 1͞10 and the 11͞2 directions of the zinc-blende lens-shaped QDs grown on the (111) plane, the polarization degree of InN QDs is found to be significantly more, by a factor of ~50 times, sensitive to the electric field than for GaN QDs. This work demonstrates that especially the InN based QD, are suitable for manipulation of the polarization by the direct control of the dot symmetry or by externally applied electric fields.
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| 4. |
- Angelov, Angel G., 1983-
(författare)
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Methods for interval-censored data and testing for stochastic dominance
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis includes four papers: the first three of them are concerned with methods for interval-censored data, while the forth paper is devoted to testing for stochastic dominance.In many studies, the variable of interest is observed to lie within an interval instead of being observed exactly, i.e., each observation is an interval and not a single value. This type of data is known as interval-censored. It may arise in questionnaire-based studies when the respondent gives an answer in the form of an interval without having pre-specified ranges. Such data are called self-selected interval data. In this context, the assumption of noninformative censoring is not fulfilled, and therefore the existing methods for interval-censored data are not necessarily applicable.A problem of interest is to estimate the underlying distribution function. There are two main approaches to this problem: (i) parametric estimation, which assumes a particular functional form of the distribution, and (ii) nonparametric estimation, which does not rely on any distributional assumptions. In Paper A, a nonparametric maximum likelihood estimator for self-selected interval data is proposed and its consistency is shown. Paper B suggests a parametric maximum likelihood estimator. The consistency and asymptotic normality of the estimator are proven.Another interesting problem is to infer whether two samples arise from identical distributions. In Paper C, nonparametric two-sample tests suitable for self-selected interval data are suggested and their properties are investigated through simulations.Paper D concerns testing for stochastic dominance with uncensored data. The paper explores a testing problem which involves four hypotheses, that is, based on observations of two random variables X and Y, one wants to discriminate between four possibilities: identical survival functions, stochastic dominance of X over Y, stochastic dominance of Y over X, or crossing survival functions. Permutation-based tests suitable for two independent samples and for paired samples are proposed. The tests are applied to data from an experiment concerning the individual's willingness to pay for a given environmental improvement.
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| 5. |
- Bellander, Theres, 1977-
(författare)
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Ungdomars dagliga interaktion : En språkvetenskaplig studie av sex gymnasieungdomars bruk av tal, skrift och interaktionsmedier
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis explores young people's interaction with different individuals through a variety of media. Three girls and three boys aged 16–18, from an urban school, a rural school and a suburban school, were each observed for a week, at school, at home and during leisure activities. The data analysed consist of field notes, video and audio recordings, and texts written by the participants. The aim of the study is to investigate how young people’s use of language varies in relation to different contexts. Questions are asked about what activities they participate in, what media they use and how they use them, and how they express themselves orally and in writing in different contexts and through different media. The study is based in sociolinguistic theory and activity type theory. Data were collected using ethnographical methods, and analytical tools were drawn from a broadly defined field of discourse analysis. The investigation sheds light on the relationship between what young people are doing socially in any given situation and how they interact. Variation in linguistic styles is made visible by a study of the same individuals involved in different communicative activities. Young people are shown to be a heterogeneous group who engage in different sets of activities. The study questions prevailing definitions and categorisations of adolescents’ linguistic styles and use of electronic media. The outcome is a complex description of everyday interaction, which is found to be shaped by the frames for communicative activities, the technical characteristics of the media employed, and individual factors. In conversational turns, Internet chat messages and text messages, young people select resources from their individual linguistic repertoires in order to achieve specific goals or construct particular roles through their interaction.
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| 6. |
- Bergdahl, Ellinor, 1981-
(författare)
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Depression among the very old
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Emotional suffering in old age is largely caused by various psychiatric conditions, of which depression is the most common. Depression is associated with a decline in both well-being and daily functioning and reduces both morale and social capacity among the very old, which may produce high health and social costs for society. The overall aim of the thesis was to study the prevalence of depression among the very old, to identify factors associated with depression and to evaluate the prognosis of depression among the very old. In total, 363 people were evaluated for depression, 242 from an urban municipality in the year 2000 and 121 from five rural municipalities in 2002. In 2005, those still alive in the urban municipality were asked to participate again, and were therefore re-evaluated. The prevalence of depression was 27% in the urban municipality, 34% in the rural municipalities and 29% in the total sample. Of those depressed, about 67% were receiving antidepressive treatment, and of those, approximately 50% had responded to treatment. In the rural municipality, the depressed were less often treated with Selective Serotonin Re-uptake Inhibitor medications, receiving instead Tri-Cyclic Antidepressants. In the rural municipalities, only 38% of the depressed had responded to treatment. A higher proportion of women were diagnosed as depressed, 33% vs. 19%, p=0.006, although the response rate was the same for men and women. Depression was twice as common among those with dementia, 44% vs. 23%. There were discrepancies concerning associated factors between the depressed participants with dementia and those without. Experiencing the death of a child during the preceding ten years was associated with depression and independently associated with depression among men and participants with dementia. In all the studies, the depressed were less often able to go outside independently and to visit others. They also received fewer visits from others and often experienced loneliness. The great majority of those who were depressed in 2000 died during the subsequent five years, only 13 out of 65, 22%, were still alive in 2005, compared to 41% of those who were not depressed, p=0.003. Of 13 who survived, only two had recovered. Twenty-four out of 70 non-depressed people, 34%, had developed depression during the five years (2000-2005), and the total prevalence in year 2005 was 42% (35 out of 83 participants). Ten out of the 24 who had developed depression were prescribed antidepressants. Of those ten, four were regarded as responders. In the group with persistent depression, nine out of eleven were receiving antidepressants and 67% were responders. In conclusion, a large proportion of the very old suffer from under-diagnosed and undertreated depression. The response rate to treatment seems to be low, and the quality of treatment and follow-up also seems to be poor. The mortality rate among the depressed was high. The spectrum of factors associated with depression in people with dementia is different from that associated with depression among non-demented. Depression among the very old clearly emerges as a common and serious public health problem, with probably the most serious impact on quality of life. More efforts have to be made to improve the quality of assessments, treatment and research regarding depression among the very old.
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| 7. |
- Bohman, Helena
(författare)
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Trade, Knowledge and Income Distribution
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis consists of four independent essays which address two main areas of research. The first area deals with the role of income distribution in economic transactions. The first paper in the thesis, Knowing me, Knowing you, suggests a new method of incorporating income distribution into international trade analysis. The method suggested provides a way to compare the distribution of income between two countries, and this is used to proxy demand similarities between the countries in question. The article Income Distribution and the diffusion of networks analyzes the impact of income distribution on the diffusion of fixed telecommunications in Brazil by showing how income distribution affects aggregate demand. The second line of research has to do with the impact of information on international trade. Insufficient information generates transaction costs, and in order to reduce costs it may be preferable to trade with known partners. The article Everybody knows? focuses on news flows as an explanatory variable in trade models. The determinants of news flows are estimated in a gravity model and subsequently in a structural equation model of international trade. The results suggest that information flow is an important determinant of international trade, but that traditional variables used in gravity models, such as income level and distance, also can be interpreted as taking information into account. Finally, the chapter Stranger in a strange land addresses the effects of international migration on explaining international trade patterns. The results reveal that immigration to Sweden has had a positive and robust effect on Swedish exports.
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| 8. |
- Dufåker, Daniel, 1971-
(författare)
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Few particle effects in pyramidal quantum dots - a spectroscopic study
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this thesis two very similar processes have been studied, both involving excitations of particles during recombination of exciton complexes in quantum dots, reducing the energy of the emitted photon. Different exciton complexes are defined according to the number of electrons and holes in the quantum dot upon recombination. The neutral exciton complexes with one electron and one hole (X) and two electrons and two holes (2X) respectively are referred to as the exciton and the biexciton. Accordingly the charged exciton complexes consisting of two electrons and one hole (X−) and one electron and two holes (X+), respectively, are referred to as negatively and positively charged excitons, respectively. Whenever another particle is excited during the recombination of one electron-hole pair within these complexes, the result is a weak satellite peak, spectrally redshifted with respect to the main emission peak related to the exciton complex.In the first part of this thesis, described in papers 1 - 3, the first and second order exciton-LO-phonon interaction is studied with weak satellite peaks, redshifted by the LOphonon energy (ћωLO or 2ћωLO), as the signature, referred to as phonon replicas. The intensity ratio between the first order replicas and the corresponding main emission were determined from the obtained micro-photoluminescence spectra. It was found that this ratio was significantly weaker for the positively charged exciton X+ compared to the neutral exciton, X, and the negatively charged exciton, X−. This experimentally obtained result was further supported by computations. Interestingly, the computations revealed that despite that X+ displays the weakest phonon replica among the investigated complexes, it possesses the strongest Fröhlich coupling to phonons in the lattice before recombination. The spectral broadening of the phonon replicas compared to the main emission is also discussed. The origin of the exciton-LO-phonon coupling is concluded to be from within the quantum dot (QD) itself, based on a comparison between quantum dots with different barriers. In addition, the measured intensity of the second order LO-phonon replica was approximately three times stronger than predictions made with the adiabatic Huang-Rhys theory but much weaker than the two orders in magnitude enhancement that was predicted when non adiabatic effects was included.Symmetrical QDs are a requirement for achieving entangled photon emission, desired for applications within quantum cryptography. In the fourth paper we relate the emission pattern of the doubly positively charged exciton X2+ to the symmetry of the QDs. In particular the splitting between the two low-energy components was found to be a measure of the asymmetry of the QDs. The emission pattern of the doubly charged exciton may then be used as a post-growth uninvasive selection tool were high-symmetry QDs could reliably be selected.In the last paper an additional weak redshifted satellite peak in the recombination spectra is studied. The intensity of this weak satellite peak is correlated to the peak intensity of the positively charged exciton, X+, main emission peak. In addition to this photoluminescence excitation experiments and computations further support our interpretation that the satellite peak is related to the shake-up of the ground state hole in the QD that is not involved in the optical recombination. This hole is excited by Coulomb interaction to an excited state yielding a photon energy that has been reduced with the difference between the ground state and the excited state of the spectator hole.
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| 9. |
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| 10. |
- Eriksson, Martin
(författare)
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Photoluminescence Characteristics of III-Nitride Quantum Dots and Films
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- III-Nitride semiconductors are very promising in both electronics and optical devices. The ability of the III-Nitride semiconductors as light emitters to span the electromagnetic spectrum from deep ultraviolet light, through the entire visible region, and into the infrared part of the spectrum, is a very important feature, making this material very important in the field of light emitting devices. In fact, the blue emission from Indium Gallium Nitride (InGaN), which was awarded the 2014 Nobel Prize in Physics, is the basis of the common and important white light emitting diode (LED).Quantum dots (QDs) have properties that make them very interesting for light emitting devices for a range of different applications, such as the possibility of increasing device efficiency. The spectrally well-defined emission from QDs also allows accurate color reproduction and high-performance communication devices. The small size of QDs, combined with selective area growth allows for an improved display resolution. By control of the polarization direction of QDs, they can be used in more efficient displays as well as in traditional communication devices. The possibility of sending out entangled photon pairs is another QD property of importance for quantum key distribution used for secure communication.QDs can hold different exciton complexes, such as the neutral single exciton, consisting of one electron and one hole, and the biexciton, consisting of two excitons. The integrated PL intensity of the biexciton exhibits a quadratic dependence with respect to the excitation power, as compared to the linear power dependence of the neutral single exciton. The lifetime of the neutral exciton is 880 ps, whereas the biexciton, consisting of twice the number of charge carriers and lacks a dark state, has a considerably shorter lifetime of only 500 ps. The ratio of the lifetimes is an indication that the size of the QD is in the order of the exciton Bohr radius of the InGaN crystal making up these QDs in the InGaN QW.A large part of the studies of this thesis has been focused on InGaN QDs on top of hexagonal Gallium Nitride (GaN) pyramids, selectively grown by Metal Organic Chemical Vapor Deposition (MOCVD). On top of the GaN pyramids, an InGaN layer and a GaN capping layer were grown. From structural and optical investigations, InGaN QDs have been characterized as growing on (0001) facets on truncated GaN pyramids. These QDs exhibit both narrow photoluminescence linewidths and are linearly polarized in directions following the symmetry of the pyramids.In this work, the neutral single exciton, and the more rare negatively charged exciton, have been investigated. At low excitation power, the integrated intensity of the PL peak of the neutral exciton increases linearly with the excitation power. The negatively charged exciton, on the other hand, exhibits a quadratic power dependence, just like that of the biexciton. Upon increasing the temperature, the power dependence of the negatively charged exciton changes to linear, just like the neutral exciton. This change in power dependence is explained in terms of electrons in potential traps close to the QD escaping by thermal excitation, leading to a surplus of electrons in the vicinity of the QD. Consequently, only a single exciton needs to be created by photoexcitation in order to form a negatively charged exciton, while the extra electron is supplied to the QD by thermal excitation.Upon a close inspection of the PL of the neutral exciton, a splitting of the peak of just below 0.4 meV is revealed. There is an observed competition in the integrated intensity between these two peaks, similar to that between an exciton and a biexciton. The high energy peak of this split exciton emission is explained in terms of a remotely charged exciton. This exciton state consists of a neutral single exciton in the QD with an extra electron or hole in close vicinity of the QD, which screens the built-in field in the QD.The InGaN QDs are very small; estimated to be on the order of the exciton Bohr radius of the InGaN crystal, or even smaller. The lifetimes of the neutral exciton and the negatively charged exciton are approximately 320 ps and 130 ps, respectively. The ratio of the lifetimes supports the claim of the QD size being on the order of the exciton Bohr radius or smaller, as is further supported by power dependence results. Under the assumption of a spherical QD, theoretical calculations predict an emission energy shift of 0.7 meV, for a peak at 3.09 eV, due to the built-in field for a QD with a diameter of 1.3 nm, in agreement with the experimental observations.Studying the InGaN QD PL from neutral and charged excitons at elevated temperatures (4 K to 166 K) has revealed that the QDs are surrounded by potential fluctuations that trap charge carriers with an energy of around 20 meV, to be compared with the exciton trapping energy in the QDs of approximately 50 meV. The confinement of electrons close to the QD is predicted to be smaller than for holes, which accounts for the negative charge of the charged exciton, and for the higher probability of capturing free electrons. We have estimated the lifetimes of free electrons and holes in the GaN barrier to be 45 ps and 60 ps, in consistence with excitons forming quickly in the barrier upon photoexcitation and that free electrons and holes get trapped quickly in local potential traps close to the QDs. This analysis also indicates that there is a probability of 35 % to have an electron in the QD between the photoexcitation pulses, in agreement with a lower than quadratic power dependence of the negatively charged exciton.InN is an attractive material due to its infrared emission, for applications such as light emitters for communication purposes, but it is more difficult to grow with high quality and low doping concentration as compared to GaN. QDs with a higher In-composition or even pure InN is an interesting prospect as being a route towards increased quantum confinement and room temperature device operation. For all optical devices, p-type doping is needed. Even nominally undoped InN samples tend to be heavily n-type doped, causing problems to make pn-junctions as needed for LEDs. In our work, we present Mg-doped p-type InN films, which when further increasing the Mg-concentration revert to n-type conductivity. We have focused on the effect of the Mg-doping on the light emission properties of these films. The low Mg doped InN film is inhomogeneous and is observed to contain areas with n-type conductivity, so called n-type pockets in the otherwise p-type InN film. A higher concentration of Mg results in a higher crystalline quality and the disappearance of the n-type pockets. The high crystalline quality has enabled us to determine the binding energy of the Mg dopants to 64 meV. Upon further increase of the Mg concentration, the film reverts to ntype conductivity. The highly Mg doped sample also exhibits a red-shifted emission with features that are interpreted as originating from Zinc-Blende inclusions in the Wurtzite InN crystal, acting as quantum wells. The Mg doping is an important factor in controlling the conductivity of InN, as well as its light emission properties, and ultimately construct InN-based devices.In summary, in this thesis, both pyramidal InGaN QDs and InGaN QDs in a QW have been investigated. Novel discoveries of exciton complexes in these QD systems have been reported. Knowledge has also been gained about the challenging material InN, including a study of the effect of the Mg-doping concentration on the semiconductor crystalline quality and its light emission properties. The outcome of this thesis enriches the knowledge of the III-Nitride semiconductor community, with the long-term objective to improve the device performance of III-Nitride based light emitting devices.
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