Användandet av temporära upplevelser och exklusivitet har sett en ökning inom moderna Games-as-a-Service spel (GaaS-spel). Några exempel på detta är battle-pass i multiplayer-spel, konserter i Fortnite och viktiga narrativa event. Nytt innehåll kan vara limiterat till att endast kunna upplevas under specifika perioder, och sedan vara otillgängligt under en obestämd tid. Denna undersökning ämnar då att se hur spelare upplever ett spel huvudsakligen designat kring dessa aspekter. För att undersöka detta har vi skapat ett narrativt spel, som är uppdelat i sju delar. De sju delarna spelas av frivilliga deltagare under en veckas tid. Varje dag släpps en ny del som bara är tillgänglig under den dagen. En kontrollgrupp spelar delarna i sin egen takt, för att vi sedan ska kunna göra en jämförelse mellan de två grupperna. Deltagarna på de kvalitativa intervjuerna hade generellt en positiv bild på spelet självt, men flera svarade att deras spelupplevelse av olika anledningar påverkades negativt av användningen av temporära upplevelser och exklusivitet. Dessa anledningar tas upp i resultatet och diskuteras sedan för att dra slutsatsen att upplägget generellt hade en negativ påverkan på spelupplevelsen, men även potential för positiv påverkan. Vi diskuterar även de brister som uppkom under undersökningen, och potentiella åtgärder. Resultatet och kunskapen vi fått ut av undersökningen anser vi kan användas för framtida forskning inom ämnet, och inom design av GaaS-spel. / The usage of temporary experiences and exclusivity has increased within modern Games-as-a-Service games (GaaS-games). Some examples of this include battle passes in multiplayer games, virtual concerts in Fortnite and important narrative events. New content can be limited to only be experienced during specific time periods, and then be unavailable indefinitely. This study explores how a game designed around these ideas affects the player experience. To test this we developed a narrative game split into seven parts. These parts are played by willing participants during a week. Every day during the week a part of the game is released, and that part is only available during the day it was released. A control group will get to play the game without these time constraints at their own pace. We later do a comparison between these two groups. Participants in the qualitative interviews had a generally positive experience with the game itself, but several answered that their experience with the game for different reasons were affected negatively by the use of temporary experiences and exclusivity. These reasons are brought up in the results and are then discussed to draw the conclusion that the model had a generally negative effect on the experience, but also has the potential for a positive effect. We also discuss the flaws that came up during the study, and potentiel remedies. We believe that the results and knowledge we have gathered from this study can be used for further research in the subject, and also the design of GaaS-games.

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Nous avons obtenu des angles de rotation Faraday (RF) allant jusqu'à 19° par orientation optique d'un gaz d'électrons dans GaAs de type n inclus dans une microcavité (Q=19000), sans champ magnétique. Cette forte rotation est obtenue en raison des multiples allers-retours de la lumière dans la cavité. Nous avons également démontré la commutation optique rapide de la RF à l'échelle sub-microseconde en échantillonnant le signal de RF sous excitation impulsionnelle mono-coup. De la dépolarisation de la RF en champ magnétique transverse, nous avons déduit un temps de relaxation de spin de 160 ns. Le concept de section efficace de RF, coefficient de proportionnalité entre l'angle RF, la densité de spin électronique, et le chemin parcouru, a été introduit. La section efficace de RF, qui définit l'efficacité du gaz d'électrons à produire une RF, a été estimée quantitativement, et comparée avec la théorie. Nous avons également démontré la possibilité de mesurer de manière non destructive l'aimantation nucléaire dans GaAs-n, via la RF amplifiée par la cavité. Contrairement aux méthodes existantes, cette détection ne nécessite pas la présence d'électrons hors équilibre. Par cette technique nous avons étudié la dynamique de spin nucléaire dans GaAs-n avec différents dopages. Contrairement à ce qu'on pourrait attendre, le déclin de la RF nucléaire est complexe et consiste en deux composantes ayant des temps de relaxation très différents. Deux effets à l'origine de la RF nucléaire sont identifiés: le splitting de spin de la bande de conduction, et la polarisation en spin des électrons localisés, tous deux induits par le champ Overhauser. Le premier effet domine la RF nucléaire dans les deux échantillons étudiés, tandis que la RF induite par les électrons localisés n'a été observée que dans l'échantillon métallique. / We obtained Faraday rotation (FR) up to 19° by using optical orientation of electron gas in n-doped bulk GaAs confined in a microcavity (Q=19000), in the absence of magnetic field. This strong rotation is achieved because the light makes multiple round trips in the microcavity. We also demonstrated fast optical switching of FR in sub-microsecond time scale by sampling the FR in a one-shot experiment under pulsed excitation. From the depolarization of FR by a transverse magnetic field, we deduce electron spin relaxation time of about 160 ns. A concept of FR cross-section as a proportionality coefficient between FR angle, electron spin density and optical path is introduced. This FR cross-section which defines the efficiency of spin polarized electrons in producing FR was estimated quantitatively and compared with theory. We also demonstrated non-destructive measurement of nuclear magnetization in n-GaAs via cavity enhanced FR. In contrast with the existing optical methods, this detection scheme does not require the presence of detrimental out-of-equilibrium electrons. Using this technique, we studied nuclear spin dynamics in n-GaAs with different doping concentrations. Contrary to simple expectation, the nuclear FR is found to be complex, and consists of two components with vastly different time constants. Two effects at the origin of FR have been identified: the conduction band spin splitting and the localized electron spin polairzation both induced by the Overhauser field. The first effect dominates the FR in both studied samples, while the FR induced by the localized electrons has been observed only in the metallic sample.

In schwach gekoppelten Halbleiterübergittern können die Elektronen resonant von dem untersten Subband eines Quantentopfes in verschiedene höhere Subbänder des benachbarten Topfes durch die Potenzialbarriere tunneln. In stark dotierten Übergittern kann sich eine Ladungsakkumulationsschicht im Übergitter ausbilden, die es in zwei Felddomänen mit verschiedenen Feldstärken teilt. Aus der detaillierten Untersuchung des Stromverhaltens bei schnellen Spannungsänderungen konnten wichtige Erkenntnisse über die Dynamik der Akkumulationsschicht gewonnen werden, die zum besseren Verständnis von selbstgenerierten Stromoszillationen beitragen. Die beobachteten Stromoszillationen liegen in einem Frequenzbereich von einigen hundert kHz bis zu einigen GHz. Es werden zwei Oszillationsmoden ausführlich beschrieben und gezeigt, wie man sie unterscheiden kann. Die erste Mode tritt bei Proben mit einer gut leitenden Kontaktschicht und moderater Dotierung auf, bei denen die Feldverteilung im Übergitter instabil ist. Die zweite Mode kann dagegen auch bei stark dotierten Übergittern auftreten. Die Voraussetzung ist, dass die Emitterkontaktschicht einen genügend großen spezifischen Widerstand besitzt. Mit dem dargestellten Escape-Time-Modell kann man aus den Übergitterparametern die Oszillationsfrequenzen und die zu erwartenden Stromdichten in den verschiedenen Plateaus abschätzen. Weiterhin wird gezeigt, wie sich die äußere Beschaltung auf die Eigenschaften auswirkt. Durch den Einbau des Übergitters in einen Resonator können diskrete Frequenzen mit einem konstanten Frequenzabstand erzeugt werden. In der Arbeit wird auch der Einfluss von DX-Zentren in den Kontaktschichten beschrieben, welche die Eigenschaften der Proben bei tiefen Temperaturen stark beeinträchtigen können. Durch die Verbesserung der Probeneigenschaften oszilliert der Strom in den Übergittern auch bei Raumtemperatur. Die Frequenz ist mit Hilfe der angelegten Spannung innerhalb eines Plateaus kontinuierlich um bis zu einem Faktor vier durchstimmbar. Es wird die Verwendung von Oszillatoren, basierend auf schwach gekoppelten Halbleiterübergittern, als Bauelement für die Nachrichtenübermittlung vorgeschlagen. / In weakly coupled semiconductor superlattices, the electrons can resonantly tunnel from the first subband of a quantum well into a higher subband of the adjacent well. In highly doped superlattices, a charge accumulation layer can be formed, which divides the superlattice in two field domains of different field strengths. From detailed investigations of the current transients after fast voltage switches, one can obtain important insights into the dynamics of the accumulation layer, which is important for the understanding of self-sustained current oscillations. The frequencies of the resulting current oscillations of the investigated samples are in the range between several hundred kHz and a few GHz. Two possible oscillation modes and their identification from the oscillation characteristics are described. The first mode is observed in samples with contacts with a small resistance and moderately doped superlattices with an unstable field distribution. The second mode appears, if the resistance of the emitter contact layer is sufficiently large and a depletion layer can be injected. A semiclassical model is introduced for the estimation of the oscillation frequencies and the current density in the different plateaus from the superlattice parameters. Finally, the influence of the electrical circuit on the properties of the oscillations will be shown. If the superlattice is put into a resonator, discrete frequencies with constant distances are observed. In this thesis also the influences of DX-centers in the contact layers are described, which can significantly alter the properties of the samples at low temperatures. By applying a larger voltage or by illumination, the contact resistance can be recovered to a common value. Due to the improvement of the sample parameters, the samples also oscillate at room temperature and above. The frequency within a plateau is continuously tunable by a factor of two to four. An application as a tunable oscillator device for wireless and optical communication is proposed.

In der Arbeit werden die mikrostrukturellen Eigenschaften von an (110)-Flächen orientierten Heterostrukturen auf GaAs-Substraten mittels verschiedener Techniken der Transmissionselektronenmikroskopie untersucht. Kubisch flächenzentrierte (Al,Ga)As/AlAs/GaAs Mehrschichtstrukturen auf GaAs(110) weisen in orthogonalen Richtungen parallel zur Substratoberfläche verschiedene Mechanismen zur Aufnahme der Verspannungen aufgrund von Fehlanpassungen auf. Defektfreie Strukturen sind durch eine geeignete, kurz periodische AlAs/GaAs-Überstruktur erfolgreich realisiert worden. Abschließend sind künstliche Defekte per Nanoindentation in den defektfreien Proben erzeugt worden, um die Auswirkung kurzperiodischer Übergitter zu prüfen. Das System aus hexagonal dicht gepacktem MnAs auf GaAs(110) zeichnet sich durch anisotrope Gitterfehlanpassung von -7.5% und 0.7% entsprechend der [11-20] und der [0001] Richtungen aus. Eine Benetzungsschicht, die der Entstehung von Inseln vorausgeht, wird beobachtet, was das Stranski-Krastanov-Wachstum von MnAs belegt. Die Dehnung durch die Gitterfehlpassung von 0.7% wird elastisch eingebaut, während die Spannung durch die Gitterfehlanpassung in der senkrechten [11-20] Richtung durch die Entstehung einer periodischen Anordnung, vollständiger Gitterfehlanpassungsversetzungen abgebaut wird, die sich von der Grenzfläche entfernt im MnAs-Gitter befinden. Das aus der Versetzungsanordnung resultierende Dehnungsfeld ist auf eine Dicke von 3.4 nm um die Grenzfläche beschränkt. Eine atomare Struktur der Grenzfläche wird basierend auf dem Vergleich von HRTEM-Aufnahmen und Simulationen vorgeschlagen. CoAl-Legierungen in der B2-Phase sind zum Vergleich auf (001) und auf (110) orientierten GaAs-Substraten hergestellt worden. Beide Fälle weisen die Koexistenz der B2-Phase und der ungeordneten, kubisch raumzentrierten Variante auf. Die Unordnung wird teilweise durch die epitaktische Dehnung und teilweise durch Diffusion von Punktdefekten hervorgerufen. / In the work, we systematically investigate the microstructural properties of (110) oriented heterostructures on GaAs substrates by means of different transmission electron microscopy techniques. Fcc-type (Al,Ga)As/AlAs/GaAs multilayer structure on GaAs (110) presents different mismatch strain accommodation mechanisms along the perpendicular in-plane directions. Defect-free structures are successfully acquired by an appropriate type of AlAs/GaAs short period superlattice. Finally, artificial defects are intentionally produced by nano-indentation to the defect-free sample to verify the effect of short period superlattices. Hcp-type MnAs on GaAs (110) system is characterized by anisotropic lattice mismatches of -7.5% and 0.7% along the [11-20] and [0001] direction, respectively. A wetting layer is observed prior to the formation of islands, indicating a Stranski-Krastanov growth mode of MnAs. The strain corresponding to the 0.7% lattice misfit is accommodated elastically, whereas the mismatch stress along perpendicular [11-20] direction is relived by the formation of a periodic array of perfect misfit dislocations with a stand-off position in MnAs lattice. The long range strain field associated with the dislocation array is constrained at the interface within a thickness of about 3.4 nm. An interfacial atomic configuration is also proposed based on the comparison between HRTEM image and the simulations. B2-type CoAl alloys are realized on (001) and (110) oriented GaAs substrates for comparison. They are both characterized by a coexistence of B2 phase and its disordered version bcc phase. The disordering is induced partially by the epitaxial strain and partially by the diffusion of point defects.

Devido à inconfiabilidade do modelo EM-X?, no cálculo da energia total, consideramos uma correção na densidade de carga \"muffin-tin\". Com esta correção podemos ajustar a energia total, a partir de parâmetros definidos na teoria. O objetivo deste trabalho é o estudo da curva da energia total associada ao estado excitado do sistema GaAs: AsGa, quando o átomo substitucional de As se desloca na direção . Partindo de cálculos de primeiros princípios (LARGE UNIT CELL APPROACH), reproduzimos a curva da energia total do estado fundamental. A partir dos parâmetros encontrados na correção não \"muffin-tin\" da densidade de carga, calculamos a curva do estado excitado utilizando o conceito de estado de transição de Slater. Nossos resultados mostraram que o efeito Jahn-TeIler não ocorre para defeitos tipo antisítio. Vimos também que a curva do comportamento dos autovalores com o deslocamento do átomo substitucional, está de acordo com cálculos recentes encontrados na literatura. / Since total energy calculations within the Multiple Scattering-X? model are not reliable, a non \"muffin-tin\" correction to the charge density has been considered. With this correction the total energy can be adjusted through parameters defined in the theory. The aim of this work is to study the total energy curve of the excited state of the GaAs: AsGa system when the arsenic substitutional atom is displaced in the direction. As a first step, the ground-state total energy curve obtained from first-principles calculations (LARGE UNIT CELL APPROACH) was reproduced. From the parameters found for the non \"muffin-tin\" charge density corrections, we have calculated the excited-state total energy curve by using the Slater transition-state concept. Our results show that the Jahn-Teller effect is not expected to occur for antisite-like defects. Moreover, the obtained behavior of the eigenvalues with displacement of the substitutional atom is in fairly good agreement with recent theoretical calculations found in the literature.

L’amélioration des performances des détecteurs (au niveau de la résolution en énergie et de la résolution spatiale) pour la radiographie X médicale par l’utilisation d’un semi-conducteur montre l’intérêt de remplacer les détecteurs à base de cristaux scintillateurs (majorité des systèmes commerciaux) par un détecteur à base de semi-conducteur. Avec une perspective de respect environnemental, ces travaux portent sur le développement d’une nouvelle génération de détecteurs à base de semi-conducteur, différent du CdTe, pour l’imagerie médicale de rayons X fonctionnant en mode comptage, ce qui permet la réduction de la dose de rayonnement envoyée sur le patient. Deux axes de recherches en découlent, avec le choix d’un nouveau matériau semi-conducteur, le GaAs semi-isolant et d’une nouvelle géométrie de détection, la géométrie 3D.Ces travaux ont consisté à évaluer expérimentalement le semi-conducteur, afin de choisir un matériau (fournisseur, croissance) et une électrode métallique qui ont la capacité de compter des photons. Puis, la structure de détection, au travers de caractérisations des procédés technologiques nécessaires pour la réalisation de la géométrie 3D (usinage des électrodes, dépôt des électrodes, connexion à un circuit électronique) et de la validation du concept avec un dispositif de test, a été également étudiée. Enfin, les premiers résultats d’un détecteur 3D à base de GaAs semi-isolant, montrant la concrétisation de ces objectifs, sont proposés. / In X-ray medical imaging, semi-conductors tend to replace scintillator crystals (most of the commercial devices), thank to their higher spatial resolution and energy resolution. Counting mode is another tendency, because it allows reducing the radiation dose delivered to the patient. This work aims at developing a new generation of semi-conductor detectors, different from CdTe / CdZnTe for environmental concerns, and associated with a new detection structure (3D geometry). Semi-insulating GaAs from specific growth and supplier, with adapted metallic electrodes, shows the ability to count photons. Then, a proof of concept of the 3D geometry is provided, through the characterization of electrodes machining in bulk material, metal deposition and connection to a read-out electronic circuit. Finally, the achievement of these objectives is reflected in the preliminary characterization of 3D detector based on semi-insulating GaAs.

Devido à inconfiabilidade do modelo EM-X?, no cálculo da energia total, consideramos uma correção na densidade de carga \"muffin-tin\". Com esta correção podemos ajustar a energia total, a partir de parâmetros definidos na teoria. O objetivo deste trabalho é o estudo da curva da energia total associada ao estado excitado do sistema GaAs: AsGa, quando o átomo substitucional de As se desloca na direção . Partindo de cálculos de primeiros princípios (LARGE UNIT CELL APPROACH), reproduzimos a curva da energia total do estado fundamental. A partir dos parâmetros encontrados na correção não \"muffin-tin\" da densidade de carga, calculamos a curva do estado excitado utilizando o conceito de estado de transição de Slater. Nossos resultados mostraram que o efeito Jahn-TeIler não ocorre para defeitos tipo antisítio. Vimos também que a curva do comportamento dos autovalores com o deslocamento do átomo substitucional, está de acordo com cálculos recentes encontrados na literatura. / Since total energy calculations within the Multiple Scattering-X? model are not reliable, a non \"muffin-tin\" correction to the charge density has been considered. With this correction the total energy can be adjusted through parameters defined in the theory. The aim of this work is to study the total energy curve of the excited state of the GaAs: AsGa system when the arsenic substitutional atom is displaced in the direction. As a first step, the ground-state total energy curve obtained from first-principles calculations (LARGE UNIT CELL APPROACH) was reproduced. From the parameters found for the non \"muffin-tin\" charge density corrections, we have calculated the excited-state total energy curve by using the Slater transition-state concept. Our results show that the Jahn-Teller effect is not expected to occur for antisite-like defects. Moreover, the obtained behavior of the eigenvalues with displacement of the substitutional atom is in fairly good agreement with recent theoretical calculations found in the literature.