This work focuses on device design and process integration of high-performance Ge-based devices for CMOS applications and beyond. Here we addressed several key challenges towards Ge-based devices, such as, poor passivation, underperformance of nMOSFETs, and incompatibility of fragile Ge wafers for mass production. We simultaneously addressed the issues of bulk Ge and passivation for pMOSFETs, by fabricating Si-capped epitaxial Ge:C(C<0.5%) devices. Carbon improves the crystalline quality of the channel, while Si capping prevents GeOx formation, creates a quantum well for holes and thus improves mobility. Temperature-dependent characterization of these devices suggests that Si cap thickness needs to be optimized to ensure highest mobility. We developed a simple approach to grow GeO₂ by rapid thermal oxidation, which provides improved passivation, especially for nMOSFETs. The MOSCAPs with GeO₂ passivation show ~10× lower Dit (~8×10¹¹ cm⁻²eV⁻¹) than that of the HF-last devices. The Ge (111) nMOSFETs with GeO₂ passivation show ~2× enhancement in mobility (~715 cm²V⁻¹s⁻¹ at peak) and ~1.6× enhancement in drive current over control Si (100) devices. For improved n⁺/p junctions, we proposed a simple technique of rapid thermal diffusion from "spin-on-dopants" to avoid implantation damage during junction formation. These junctions show a high ION/IOFF ratio (~10⁵⁻⁶) and an ideality factor of ~1.03, indicating a low defect density, whereas, ion-implanted junctions show higher Ioff (by ~1-2 orders) and a larger ideality factor (~1.45). Diffusion-doped and GeO₂-passivated Ge(100) nMOSFETs show a high ION/IOFF ratio (~10⁴⁻⁵) , a low SS (111 mV/decade), and a high [mu]eff (679 cm²V⁻¹s⁻¹ at peak). Moreover, diffusion-doped Ge (111) nMOSFETs show even higher [mu]eff (970 cm²V⁻¹s⁻¹ at peak) that surpasses the universal Si mobility at low Eeff. For Beyond CMOS devices, we investigated Mn-doped Ge:C-on-Si (100), a novel Si-compatible ferromagnetic semiconductor. The investigation suggests that the magnetic properties of these films depend strongly on crystalline structure and Mn concentration. On a different approach, we developed LaOx/SiOx barrier for Spin-diodes that reduces contact resistance by ~10⁴, compared to Al₂O₃ controls and hence is more conducive for spin injection. These ferromagnetic materials and devices can potentially be useful for novel spintronic devices. / text

No description available.

<p>Accurate characterization of a noisy device starts with an accurate measurement system. Measurement uncertainty and error continues to be a challenging subject as technology advances. The conventional method to noise characterization of on-wafer devices is to determine its noise parameters. To extract the noise parameters of an unpackaged device involves a sophisticated measurement system and calibration procedure. This thesis presents a new automated on-wafer noise measurement system based on Labview 8.5.1 which is used to examine measurement uncertainty for noise parameter extraction. The software program can be used and customized for a wide range of on-wafer noise measurements. This thesis covers the design and operation of the measurement system, which is then used to analyze measurement uncertainty.</p> <p>Measurement uncertainty can be due to various sources from environmental surroundings to instrument settings and the components of the system itself. In many scenarios, inaccuracies are random and cannot be completely resolved. In this thesis, a new tuner characterization technique that improves source tuner characterization is presented. Additionally, a new gain compensation technique is applied to measured noise powers that attempt to improve noise parameter extraction accuracy is proposed. The tuner characterization technique is evaluated against a current industry solution and the affects of the gain compensation technique is evaluated using a newly developed figure of merit. This research work concludes that a direct noise power correction is valid and necessary to further improve noise parameter accuracy. However, the proposed technique when applied resulted in minimal change to the overall noise parameter data. It is found that that source termination selection and total points used for fitting continue to be the major source of uncertainty for noise parameter accuracy.</p> / Master of Applied Science (MASc)

Realization of low-resistance electrical contacts on both sides of a solar cell is essential for obtaining the best possible performance. A key component of a solar cell is a metal contact on the illuminated side of the cell which should efficiently collect carriers. These contacts can be formed using an opaque metal grid/finger pattern. The metal electrode may be used alone or in combination with a broad-area transparent conductive film. This work aims at investigating the impact of the electrical contacting scheme employed in InGaN/GaN Schottky barrier solar cells on their performance. InGaN is a III-V compound semiconductor and has a tunable direct band-gap (0.7 eV to 3.4 eV) which spans most of the solar spectrum; this fact, along with other beneficial material properties, motivates the study of InGaN photovoltaic devices. A number of groups have recently investigated InGaN-based homo-junction and hetero-junction p-i-n solar cells. However, very few groups have worked on InGaN Schottky solar cells. Compared to p-n junctions, Schottky barrier solar cells are cheaper to grow and fabricate; they are also expected to improve the spectral response because of near surface depletion regions in the shorter wavelength regions. In this particular work on InGaN based solar cells, a Schottky diode structure was used to avoid the issue of highly resistive p-type InGaN. In this study, platinum (Pt) is used to form a Schottky barrier with an InGaN/GaN absorber region. Electrical and optical properties of platinum films are investigated as a function of their thickness. InGaN/GaN Schottky solar cells with platinum as the transparent conductive film are reported and their performance is evaluated as a function of the metal thickness. / Master of Science

<p>The trichromatic principle of representing color has for a long time been dominating in color imaging. The reason is the trichromatic nature of human color vision, but as the characteristics of typical color imaging devices are different from those of human eyes, there is a need to go beyond the trichromatic approach. The interest for multi-channel imaging, i.e. increasing the number of color channels, has made it an active research topic with a substantial potential of application.</p><p>To achieve consistent color imaging, one needs to map the imaging-device data to the device-independent colorimetric representations CIEXYZ or CIELAB, the key concept of color management. As the color coordinates depend not only on the reflective spectrum of the object but also on the spectral properties of the illuminant, the colorimetric representation suffers from metamerism, i.e. objects of the same color under a specific illumination may appear different when they are illuminated by other light sources. Furthermore, when the sensitivities of the imaging device differ from the CIE color matching functions, two spectra that appear different for human observers may result in identical device response. On contrary, in multispectral imaging, color is represented by the object’s physical characteristics namely the spectrum which is illuminant independent. With multispectral imaging, different spectra are readily distinguishable, no matter they are metameric or not. The spectrum can then be transformed to any color space and be rendered under any illumination.</p><p>The focus of the thesis is high quality image-acquisition in colorimetric and multispectral formats. The image acquisition system used is an experimental system with great flexibility in illumination and image acquisition setup. Besides the conventional trichromatic RGB filters, the system also provides the possibility of acquiring multi-channel images, using 7 narrowband filters. A thorough calibration and characterization of all the components involved in the image acquisition system is carried out. The spectral sensitivity of the CCD camera, which can not be derived by direct measurements, is estimated using least squares regression, optimizing the camera response to measured spectral reflectance of carefully selected color samples.</p><p>To derive mappings to colorimetric and multispectral representations, two conceptually different approaches are used. In the model-based approach, the physical model describing the image acquisition process is inverted, to reconstruct spectral reflectance from the recorded device response. In the empirical approach, the characteristics of the individual components are ignored, and the functions are derived by relating the device response for a set of test colors to the corresponding colorimetric and spectral measurements, using linear and polynomial least squares regression.</p><p>The results indicate that for trichromatic imaging, accurate colorimetric mappings can be derived by the empirical approach, using polynomial regression to CIEXYZ and CIELAB. Because of the media-dependency, the characterization functions should be derived for each combination of media and colorants. However, accurate spectral data reconstruction requires for multi-channel imaging, using the model-based approach. Moreover, the model-based approach is general, since it is based on the spectral characteristics of the image acquisition system, rather than the characteristics of a set of color samples.</p> / Report code: LiU-TEK-LIC- 2006:70

Dy-incorporated HfO₂ gate oxide with TaN gate electrode nMOS device has been developed for high performance CMOS applications in 22nm node technology. DyO /HfO bi-layer structure shows thin EOT with reduced leakage current and less charge trapping compared to HfO₂. Excellent electrical performance of the DyO-capped HfO₂ oxide n-MOSFET such as lower V[subscript TH], higher drive current, and improved channel electron mobility are reported. DyO/HfO samples also show better immunity for V[subscript TH] instability and less severe charge trapping characteristics. Its charge trapping characteristics, conduction mechanisms and dielectric reliability have been investigated in this work. As an application to memory device, HfON charge trapping layered NAND flash memory is developed and characterized. First, temperature-dependent Dy diffusion and the diffusion-driven Dy dipole formation process are discussed to clarify the origin of V[subscript TH] shift, and eventually modulate the effective work function in Dy-Hf-O/SiO₂ system. The Dy-induced dipoles are closely related to the Dy-silicate formation at the high-k/SiO₂ interfaces since the V[subscript FB] shift in Dy₂O₃ is caused by the dipole and coincides with the Dy-silicate formation. Dipole formation is a thermally activated process, and more dipoles are formed at a higher temperature with a given Dy content. The Dy-silicate related bonding structure at the interface is associated with the strength of the Dy dipole moment, and becomes dominant in controlling the V[subscript FB]/V[scubscript TH] shift during high temperature annealing in the Dy- Hf-O/SiO₂ gate oxide system. Dy-induced dipole reduces the degradation of the electron mobility. Second, to understand the reduced leakage current of the DyO/HfO sample, the effective barrier height of Dy₂O₃ was calculated from FN tunneling models, and the band diagram was estimated. The higher effective barrier height of Dy₂O₃, which is around 2.32 eV calculated from the F-N plot, accounts for the reduced leakage current in Dy incorporated HfO₂ nMOS devices. The lower barrier height of HfO₂ result in increased electron tunneling currents enhanced by the buildup of hole charges trapped in the oxide, which causes a severe increase of stress-induced leakage current (SILC), leading to oxide breakdown. However, the increased barrier height in Dy incorporated HfO₂ inhibits a further increase of the electron tunneling from the TaN gate, and trapped holes lessen the hole tunneling currents, resulting in a negligible SILC. The lower trap generation rate by the reduced hole trap density and the reduced hole tunneling of the Dy-doped HfO₂ dielectric demonstrates the high dielectric breakdown strength by weakening the charge trapping and defect generation during the stress. Based on these fundamental studies of the dielectric breakdown, modeling of time-dependent dielectric breakdown (TDDB) was done. The intrinsic TDDB of the Dy-doped HfO₂ gate oxide having 1 nm EOT is characterized by the progressive breakdown (PBD) model. At high temperature, the PBD becomes severe, since thermal energy causes carrier hopping between the localized weak spots. The voltage acceleration factor derived from the power law shows a realistic prediction in comparison with those from the 1/E model. The increase of the voltage acceleration factor at lower stress voltage is due to the lower trap generation rate in Dy- incorporated HfO₂. This voltage acceleration factor can be easily extended to include temperature dependency, and the effective activation energy derived from the power law is voltage dependent. Lastly, I studied the device characteristics of thin HfON charge-trap layer nonvolatile memory in a TaN/Al₂O₃/HfON/SiO₂/p-Si (TANOS) structure. A large memory window and fast erase speed, as well as good retention time, were achieved by using the NH₃ nitridation technique to incorporate nitrogen into the thin HfO₂ layer, which causes a high electron-trap density in the HfON layer. The higher dielectric constant of the HfON charge-trap layer induces a higher electric field in the tunneling oxide at the same voltage compared to non-nitrided films and, thus, creates a high Fowler-Nordheim (FN) tunneling current to increase the erase and programming speed. The trap-level energy in the HfON layer was calculated by using an amphoteric model. / text

Doctor of Philosophy / Department of Mechanical and Nuclear Engineering / Douglas S. McGregor / The low natural abundance and supply shortage of ³He has resulted in an increase in the cost of ³He. The increase in cost of ³He proportional counters has motived the development of low cost, high efficiency, low gamma-ray sensitivity alternative technologies. A recently developed alternative technology is the ⁶Li-based suspended foil microstrip neutron detector (SFMND) that combines the neutron-conversion and gamma-ray discrimination capabilities of ⁶Li foils with the mechanical robustness and electrical capabilities of microstrip electrodes. SFMNDs differ from Li-foil multi-wire proportional counters because the anode wires are replaced by a single microstrip electrode that improves the mechanical robustness, reduces the microphonic sensitivity, and allows for more ⁶Li foils to be incorporated within a smaller form factor. The first-ever SFMNDs containing one and five 96%-enriched, 75-µm thick ⁶Li foils were fabricated using a silicon microstrip electrode. Neutron-sensitivity testing was performed yielding measured intrinsic thermal-neutron detection efficiencies, εth, of 4.02 ± 0.04% and 14.58 ± 0.11%, respectively. High electrode capacitance and gain instability were exhibited by the silicon microstrip electrode during neutron-sensitivity testing that led to the search for an electrically-stable microstrip-electrode substrate. Schott Borofloat® 33 glass was identified as an electrically-stable substrate and microstrip electrodes were fabricated and characterized. The Schott Borofloat® 33 microstrip electrodes were electrically-stable for a minimum duration of time of approximately 23 hours and had capacitances over an order of magnitude less than the identically sized silicon microstrip electrodes. One- and five-foil SFMNDs were fabricated with a Schott Borofloat® 33 microstrip electrode. Using 96%-enriched, 75-µm thick ⁶Li foils, the one- and five-foil devices had maximum measured εth of 12.58 ± 0.15% and 29.75 ± 0.26%, respectively, with measured gamma-ray rejection ratios of 6.46 x 10⁻⁵ ± 4.32 x 10⁻⁷ and 7.96 x 10-5 ± 4.65 x 10-7 for a ¹³⁷Cs exposure rate of 50 mR hr⁻¹. Devices containing one, five, ten, and twenty 96%-enriched, 75-µm thick ⁶Li foils were simulated using MCNP6 and are theoretically capable of having εth of 18.36%, 54.08%, 65.43%, and 68.36%, respectively. The deviation between measured and simulated εth is suspected to occur due to the electric field strength distribution, electron attachment, microstrip-electrode capacitance, or any combination thereof and solutions for each of these suspected concerns are described.

The Terahertz region of the electromagnetic spectrum is the region between microwaves and infra-red, dubbed the terahertz 'gap' due to its relative underdevelopment in terms of technology. This region is marked by expensive and inconvenient sources that are bulky or that require cryogenic cooling for normal operation, therefore creating a need for cheap and easy to use terahertz sources. Carbon nanotubes have received considerable attention since their discovery due to their unique physical and electronic properties. Many applications have been proposed using especially Single-Walled Carbon Nanotubes (SWCNTs), and a number of commercial technologies exist. In this work, we have proposed to use SWCNTs as the basis for a cheap, compact and room temperature-operating Terahertz source. We have characterized the SWCNT source, and we present results on transport characteristics (I–V curves), radiation patterns, spectra, polarization as well as optical, SEM and AFM imaging. We show that the radiation spectrum is vi determined by integrated antennas coupled to the SWCNTs, and preliminary power calibration indicates that the radiated power exceeds the power predicated by the Nyquist formula.

No description available.

O presente trabalho faz inicialmente uma revisão básica a respeito de diodos controlados por porta ressaltando o método criado por Grove, e corrigido por Pierret, para a determinação da velocidade de recombinação superficial, parâmetro esse, importante na análise do desempenho do dispositivo frente a situações que tendem a degradar o funcionamento do mesmo. Em seguida, propomos a utilização de DCP\'s como sensores de radiação luminosa e possivelmente como sensor de cores. Para tanto, simulamos o comportamento de uma junção PN sob iluminação quando variamos a extensão da região de depleção associada à mesma. De acordo com essas simulações, observamos que o rendimento de conversão da energia luminosa para elétrica, em função do comprimento de onda da luz incidente, apresenta dependência com relação a extensão da região de carga espacial. Essa característica pode vir a ser usada, futuramente, na detecção seletiva de comprimentos de onda, e portanto, permitindo a discriminação de cores. A variação da largura da região de depleção nas proximidades de uma junção PN pode ser conseguida, numa estrutura do tipo DCP, através da aplicação em sua porta, de pulsos de amplitude e inclinação adequadas, de forma a levá-lo a operar em depleção profunda. Nessas condições, o valor máximo da largura da região de depleção é maior do que o seu valor máximo estacionário, podendo chegar a até 3 vezes o mesmo, conforme foi constatado por simulação, através de um software por nós desenvolvido, para uma estrutura MOS pulsada. Tal simulação forneceu-nos o campo e potencial elétricos e a concentração de portadores em função da profundidade através da resolução da equação de Poisson com condições de contorno adequadas. Dados os resultados obtidos nas simulações, a próxima etapa foi a elaboração de máscaras litográficas para construir diodos controlados por porta com diferentes geometrias, algumas sugeridas pela literatura, outras ) desenvolvidas para esse trabalho. Tais máscaras foram confeccionadas pelo CTI em Campinas e foram desenhadas através do software Microeletrônica de Etienne Sicard da universidade de Toulouse. Utilizamos as máscaras fabricadas para construir uma pastilha-teste preliminar com os diodos controlados por porta propostos. Infelizmente, nesta única corrida, tivemos curto-circuito entre porta e substrato e apenas as junções PN funcionaram a contento. Obtivemos diodos com fator de idealidade de ~1,4 e densidade de corrente reversa, no melhor dos casos, igual a 1,23.104 nA/cm² para áreas de (1000 x 1000) µm². Por outro lado, como não conseguimos DCP\'s funcionando, utilizamos transistores nMOS convencionais, fornecidos pelo Prof. João Antonio Martino, para medir a velocidade de recombinação superficial, \"velocidade de recombinação aparente\", que resultou em 5,5×106 cm/s, segundo o método proposto por Pierret. / This work presents a basic review about gate-controlled diodes (GCD) mainly on the method created by Grove and corrected by Pierret, for measuring the surface recombination velocity that is an important parameter on the analysis of device performance. In the sequence, we propose the use of GCD\'s as light radiation sensors and, probably as color sensors. To do so, we have simulated the behavior of a PN junction under illumination, varying the depletion region length. The simulations revealed that the luminous to electrical energy conversion depends on the length of the spatial charge region. This could be used, in the future, on the selective wavelength detection, alloying color discrimination. The variation of the depletion region length in the vicinity of a PN junction can be done, in a GCD structure, by applying in its gate, a set of electrical pulses with the right characteristics, in order to drive it to the deep depletion mode. In these conditions, the maximum length of the depletion region is larger than its steady state value, reaching as much as 3 times that value, as could be determined by means of simulation of a pulsed MOS structure, in a specific software developed for that purpose. This software give us the electric field and potencial and the carrier concentration against depth into the silicon by solving the Poisson equation with the right boundary conditions. Keeping these results in mind, the next step was the project of the lithographic masks in order to explore some different geometries, some of them suggested by the literature, others developed in this work. The fabrication of those masks were done by CTI in Campinas e were designed with the software Microeletrônica by Etienne Sicard from the university of Toulouse. We have used the masks to manufacture a preliminary chip test which included gate-controled diodes.Unfortunately, in this unique run, \"short circuits\" between gate and bulk has occurred and only the PN junctions worked as expected. We have obtained diodes with ideality factor of ~1.4 and reverse current density of 1.23.104 nA/cm² in the best case for junction areas of (1000 x 1000) µm². On the other hand, as we have not got gate-controlled diodes which were working, we have used conventional nMOS transistors borrowed by Prof. João Antônio Martino. Surface recombination velocity so was measured in these nMOS transistors and resulted in 5.5.106 cm/s, according to the method proposed by Pierret.