Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 36 for “"carrier densities"”.
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Charge Transport Physics of Organic Semiconductors at High Carrier Densities
… physics in this class of materials at low carrier densities of less than 10¹⁸ to 10¹⁹ cm¯³ has been relatively well established, the physics at much higher carrier densities of 10²⁰ to 10²¹ cm¯³ remains poorly understood. In this transport regime there is on the order of one charge per …
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Quasi-Newton and Multigrid Methods for Semiconductor Device Simulation
… and the quasi-Newton methods for the scaled carrier densities and carrier densities converge locally for sufficiently smooth problems.
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Ultrafast carrier dynamics and enhanced electroabsorption in (gallium,indium)arsenide/(aluminum,indium)arsenide asymmetric double quantum well structures
… A single time constant is observed at low carrier densities indicating the holes tunnel from the narrow well (NW) to the wide well (WW) at least as fast as electrons. At high carrier densities a two component decay is observed, consistent with phase-space filling and space-charge effects …
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Nanoscale structure and transport : from atoms to devices
… to be an important limit on mobility at high carrier densities. At low carrier densities, such short-wavelength roughness results in qualitatively different mobility behavior than gradual UTSOI channel thickness fluctuations.
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Electrical transport and superconductivity in doped quantum critical ferroelectrics
… neighbourhood of quantum phase transitions in carrier-doped ferroelectrics and paraelectrics. The materials of interest are doped SrTiO3, located close to the quantum critical point at ambient pressure and doped ferroelectric BaTiO3, which may be tuned to its quantum phase transition with …
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Carrier Dynamics in Perovskite Nanocrystals
… for high-efficiency solar cells. Ultrafast carrier-phonon interactions in semiconductors represent a major loss of the excess energy of photoexcitations above the bandgap. We demonstrate approaches to suppress the relaxation process, which may allow the full photon energy to be usefully …
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Towards infrared plasmonics in graphene
… rely on controllable doping of graphene to high carrier densities in nanometer-scale structures. In this thesis, an experimental approach to generating nanoscale spatial carrier density modulation of graphene using electrolyte gates and crosslinked-PMMA screen is proposed and investigated. The …
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Quantitative photoluminescence studies in a-Si:H/c-Si solar cells
… coefficient for higher T. Simulation of carrier densities and EFn-EFp shows the high sensitivity of these variables for different Dif at Voc. Finally, the differences between a PL-I-V-curve and the I-V-characteristics from a-Si:H/c-Si solar cells are analyzed.
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Investigation of carrier dynamics in InN, InGaN, and GaAsBi by optical pump-probe techniques /
The thesis is dedicated to investigation of carrier dynamics in InN, InGaN, and GaAsBi heterostructures by using light-induced transient gratings and differential transmission techniques. The experimental studies in a wide range of excess carrier densities and temperatures revealed that …
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Optical properties of two-dimensional transition metal dichalcogenides
… and studied its exciton behaviors with different carrier densities and dielectric environments through PL measurements with the help of electrochemical gating and non-ionic solvent immersion. Our findings are helpful to understand better the tightly bound excitons in low-dimensional systems and to …
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Spin dynamics of bulk and quasi-two-dimensional metal halide based perovskite semiconductors
… between Dr Ravichandran Shivanna and me. For carrier densities above ~10<sup>15</sup> cm<sup>-3</sup>, the room temperature exciton depolarisation rate increases with exciton density, showing that many-body interactions outcompete the precessional motional narrowing spin relaxation that was …
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Theory of terahertz intervalence band polaritons and antipolaritons.
… are obtained and investigated for different carrier densities and cavity configurations. Recently, intersubband based THz polariton emitters and THz quantum cascade lasers are attracting major research interest due to their great importance in applications such as THz imaging, spectroscopy as …
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Charge-carrier transport in amorphous organic semiconductors
… small bandwidth leads to localization of charge carriers and electron-hole pairs, called excitons. Thus, the charge-carrier mobility in organic semiconductors is generally much smaller than in their covalently-bonded, highly-ordered crystalline semiconductor counterparts. Indeed, one major …
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Temperature-Dependent High-Speed Modulation and Wavelength Conversion Using Quantum-Well Lasers
… theoretical fits to the data and predicted carrier densities are obtained using a many-body gain model. The modulation response due to optical pumping at 1.3 mum wavelength is compared with the electrical response in order to remove the influence of electrical parasitics. The temperature …
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Application of quantum Monte Carlo methods to homogeneous electron and electron-hole systems
… and pair correlation functions are obtained over densities $r_s = 0.5 – 20$ a.u. and the full range of spin-polarisation, allowing comparison with the Perdew-Zunger interpolation scheme used in local spin density approximation exchange-correlation functionals. Following this, an impurity is added …
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Surface transfer doping of diamond for power electronics
… conductive 2D hole sheet at the surface with carrier densities going up to 10¹⁴ cm⁻². Surface transfer doping using stable high electron affinity transition-metal oxides (TMO) such as WO₃ in conjunction with the novel contact-first process explored in this work shows great promise on advancing …
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High Pressure Quantum Oscillation Study of BiTeI and Bi2Te3
… determine model parameters. Based on this model, carrier densities for the samples were calculated and there was good agreement with Hall effect measurements. The phase of the oscillations showed that both Fermi surfaces have a Berry phase of $\pi$ associated with them, consistent with theoretical …
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Theory of graphene transport properties
… samples, while having higher mobility at high carrier density, will manifest more strongly insulating (and thus effectively more disordered) behavior as the carrier density is lowered compared with lower quality samples (with higher disorder), which exhibit an approximate resistivity saturation …
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Thermal and Optical Simulations of Vertical Cavity Surface Emitting Lasers
… lattice temperature model is derived based on carrier transport and the conservation of energy. A novel treatment is applied to model distributed Peltier heat at a heterojunction by use of a Monte Carlo simulation. Peltier heat is found to be a major heat contributor, and it results in a rapid …
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Semiconductor Laser Device-Level Characteristics
<p>High-speed modulations of the semiconductor lasers are highly desirable in cost-effective optical communication systems. Developing the experimental setups to extract the characteristics of the semiconductor lasers is vital to the future of the optical research projects. In this thesis, …
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