abstract: This PhD thesis consists of three main themes. The first part focusses on modeling of Silver (Ag)-Chalcogenide glass based resistive memory devices known as the Programmable Metallization Cell (PMC). The proposed models are examined with the Technology Computer Aided Design (TCAD) simulations. In order to find a relationship between electrochemistry and carrier-trap statistics in chalcogenide glass films, an analytical mapping for electron trapping is derived. Then, a physical-based model is proposed in order to explain the dynamic behavior of the photodoping mechanism in lateral PMCs. At the end, in order to extract the time constant of ChG materials, a method which enables us to determine the carriers’ mobility with and without the UV light exposure is proposed. In order to validate these models, the results of TCAD simulations using Silvaco ATLAS are also presented in the study, which show good agreement. In the second theme of this dissertation, a new model is presented to predict single event transients in 1T-1R memory arrays as an inverter, where the PMC is modeled as a constant resistance while the OFF transistor is model as a diode in parallel to a capacitance. The model divides the output voltage transient response of an inverter into three time segments, where an ionizing particle striking through the drain–body junction of the OFF-state NMOS is represented as a photocurrent pulse. If this current source is large enough, the output voltage can drop to a negative voltage. In this model, the OFF-state NMOS is represented as the parallel combination of an ideal diode and the intrinsic capacitance of the drain–body junction, while a resistance represents an ON-state NMOS. The proposed model is verified by 3-D TCAD mixed-mode device simulations. In order to investigate the flexibility of the model, the effects of important parameters, such as ON-state PMOS resistance, doping concentration of p-region in the diode, and the photocurrent pulse are scrutinized. The third theme of this dissertation develops various models together with TCAD simulations to model the behavior of different diamond-based devices, including PIN diodes and bipolar junction transistors (BJTs). Diamond is a very attractive material for contemporary power semiconductor devices because of its excellent material properties, such as high breakdown voltage and superior thermal conductivity compared to other materials. Collectively, this research project enhances the development of high power and high temperature electronics using diamond-based semiconductors. During the fabrication process of diamond-based devices, structural defects particularly threading dislocations (TDs), may affect the device electrical properties, and models were developed to account of such defects. Recognition of their behavior helps us understand and predict the performance of diamond-based devices. Here, the electrical conductance through TD sites is shown to be governed by the Poole-Frenkel emission (PFE) for the temperature (T) range of 323 K ˂ T ˂ 423 K. Analytical models were performed to fit with experimental data over the aforementioned temperature range. Next, the Silvaco Atlas tool, a drift-diffusion based TCAD commercial software, was used to model diamond-based BJTs. Here, some field plate methods are proposed in order to decrease the surface electric field. The models used in Atlas are modified to account for both hopping transport in the impurity bands associated with high activation energies for boron doped and phosphorus doped diamond. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2017

Ce travail de thèse porte sur une série d’échantillons de composition nominale AgBiSe2-xSx (avec x= 0 à 2), appartenant à la famille des chalcogénures ternaires de type I-V-VI₂. Les analyses structurales et thermiques ont mis en évidence une solution solide complète sans gap de miscibilité, et des transitions de phase pour toutes les compositions. Nous avons pu obtenir des composés monophasés à la fois des phases hexagonale et cubique, et notre étude de DRX en température à mis en évidence une phase rhomboédrique pour certaines compositions (x=1 à 2 dans AgBiSexS2-x). Les résultats de DSC ont confirmé la présence de transitions de phase pour toutes les compositions, avec un déplacement des températures de transition en fonction de la fraction de soufre/sélénium. Notre étude de DRX sous pression de l’échantillon AgBiSe₂ a montré une transition de phase induite par la pression d’une phase hexagonale à rhomboédrique puis cubique. Suite à cette observation, l’application d’une pression chimique, par la substitution de 30% du Bi par du Sb a été utilisée avec succès pour stabiliser la phase cubique pour toutes les compositions. Le dopage par Nb des échantillons substitués par l’antimoine l’a pas eu d’influence sur la nature des phases stables à l’ambiante en comparaison aux échantillons non dopés. Nous avons ensuite étudié l’influence du dopage sur les propriétés de transport. Les valeurs négatives de S pour toutes les compositions indiquent un comportement de semi-conducteur de type n dans la gamme (50-300K). Par ailleurs, nos mesures ont montré à a fois de très faibles valeurs de κ mais aussi une décroissance de ∣S∣ et ρ avec l’augmentation de la fraction de Nb. Ces résultats devraient permettre d’optimiser le facteur de puissance pour améliorer les valeurs de ZT. Enfin, une étude en collaboration avec une équipe chinoise a permis d’obtenir une valeur de ZT de 1.3 à 890K dans un composé AgPbmSnSe₂. / Here, we report on a series of samples with nominal compositions AgBiSe2-xSx (with x= 0 to 2) belonging to the class of ternary chalcogenides of type I-V-VI₂. The structural and thermal analysis result shows a complete solid solution without miscibility gap and phase transitions for all compositions. We have succeeded in obtaining single phase compounds, of both hexagonal and cubic phase, and the high temperature XRD study showed the rhombohedral phase too for selected compositions (x=1 to 2 in AgBiSexS2-x). The DSC results confirmed the presence of the phase transitions for all compositions, with a shift of the temperature of transition as a function of the sulfur/selenium fraction. The high pressure XRD investigation of the compound AgBiSe₂ showed a pressure induced phase transition from hexagonal-to-rhombohedral-to-cubic phase. In this respect, chemical pressure with 30% Sb on the Bi site has been successfully applied to stabilize the cubic phase for all compositions. Nb doping in the Sb-substituted samples does not show any change in the phase behavior at RT in comparison with the undoped samples. The influence of doping on transport properties was analyzed. The negative value of S for all compositions indicates n-type semiconducting behavior over the range (50-300K). Further, the results not only shows very low value of κ but the ∣S∣ and ρ value also decreases for each composition from Nb fraction 0.02 to 0.04. This gives us the opportunity to optimize the power factor in order to improve the ZT value. At last, collaborative study with Chinese team showed that ZT of 1.3 at 890 K can be achieved for AgPbmSnSe2+m (m = 50).

This study aimed to investigate methods for determining the temperature dependence of the refractive index and absorption of IR-transparent materials through literary studies and experimental tests. Results from the experimental trials were hard to obtain due to the inherent difficulty of measuring optical properties and yielded only temperature trends of transmittance and reflectance. Despite this, the results could be used for speculation regarding the temperature dependency of the refractive index and the absorption which provides insights into the optical properties of a material. There are several suggestions to improve measurements using this method for future work to be able to determine precise values of the properties. Two additional methods have been reviewed with a literary study, the minimum deviation prism method and the improved Swanepoel thin film method. Both methods are regarded as promising candidates for determining refractive index and its temperature dependence with good accuracy. However, the improved Swanepoel method stands out as the more promising candidate. The determination of absorption and its temperature dependence is established to be inherently hard to determine with the experimental method and the two researched methods, thus suggestions for measuring the absorption in future work are given.