Spreading Resistance Research Articles

Analytical expressions for spreading resistance in lossy media and their application to the calibration of scanning microwave microscopy.

This paper presents the analytical derivation of spreading resistance expressions for diverse geometries of a conducting probe submerged in a lossy medium. Resulting equations can be used to calibrate scanning impedance/scanning microwave microscopes operating in liquid. The expressions are systematically validated through numerical and experimental methods for the calibration of an inverted Scanning Microwave Microscope (iSMM) when operating in a lossy saline medium, such as Dulbecco's Modified Eagle Medium (DMEM), a widely used medium for supporting the growth of biological cells. The calibration process within DMEM plays an important role in the quantitative local evaluation of electromagnetic properties of biological samples under physiological conditions. Additionally, measurements are performed in distilled water for comparative analysis.

Cephalosporin susceptibility of Staphylococcus aureus strains isolated from commercial rabbit and goats farms in Spain.

Antimicrobial drug resistance is an important problem that challenges veterinary clinicians to provide effective treatments without further spreading resistance to other animals and people. The most commonly used pharmacodynamic parameter to define potency of antimicrobial drugs is minimum inhibitory concentration (MIC). The aim of this study was to evaluate the antibiotic susceptibility of thirty-six strains of Staphylococcus aureus isolated from dairy goats with mastitis and rabbits with chronic staphylococcosis. Four cephalosporins were tested: cephalexin, cephalotin, cefonicid and ceftiofur. MIC tests were performed according to the microdilution broth method. The calculated values of sensitivity in goats and rabbits were 66.67% and 72.22% for cephalexin, 72.22 % and 94.44% for cefonicid, 77.78% and 94.44% for cephalotin and 77.78% and 100% for ceftiofur, respectively. For all antibiotics, MIC90 of S. aureus from rabbits were lower than MIC90 from goats. These data suggest that more antibiotics are used in goat milk production than in rabbit farming. According to MIC values obtained in this study, ceftiofur and cephalotin may be the best option for treating S. aureus infections in lactating goats. For rabbits, ceftiofur showed lowest MIC values, therefore, it could be an alternative to treatment the infections caused by S. aureus in this species.

Nanometer-Scale Measurement of Grid Finger Electrical Conduction Pathways to Detect Series Resistance Degradation of Utility-Scale Silicon Solar Cells

We report on an electrical conduction mechanism for series resistance (Rs) degradation observed in a utility-scale photovoltaic power plant by imaging the local resistance at the Ag/Si interface of the c-Si front metallization. Scanning spreading resistance microscopy imaging with nanometer (nm) scale spatial resolution revealed that the number of point or small-area electrical contacts decreased substantially in a degraded cell compared to an unaffected cell, demonstrating the root cause of Rs degradation. The decrease in electrical contacts is likely caused by a structural change—the Ag particles in contact with the Si cell (or via a nm-thickness tunneling glass layer) aggregate into bulk Ag, and a highly resistive glass frit forms a belt shape at the Ag/Si interface. This resistive belt, with a thickness of ∼1 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m, blocks the current conduction from the cell emitter to the Ag grid. Our microscopy results help to unravel unambiguously the degradation mechanism and demonstrate an example of the multiscale characterization approach for understanding degradation in field-weathered PV module.

A Transient Resistance/Capacitance Network-Based Model for Heat Spreading in Substrate Stacks Having Multiple Anisotropic Layers

Abstract Heat spreading from local, time-dependent heat sources in electronic packages results in the propagation of temperature nonuniformities through the stack of material layers attached to the chip. Available models either predict the chip temperatures only in the steady-state or a single substrate for transient analysis, without the ability to predict the transient response in compound substrates having multiple anisotropic layers. We develop a transient resistance/capacitance network-based modeling approach capable of predicting the spatiotemporal temperature fields for this chip-on-stack geometry, accounting for in-plane heat spreading, through-plane heat conduction, and the effective convection resistance boundary conditions. The transient heat spreading resistance for an anisotropic substrate has been formulated by converting it to an effective isotropic substrate for which there is an available half-space solution. The transient heat spreading model for a step heat input to a single substrate is subsequently extended to any arbitrary transient heat input using a Fourier series and extending the half-space formulation from a step heat input to sinusoidal heat input. For obtaining the transient spreading resistance for heat inputs into multiple stacked substrates, a method has been outlined to convert the multisubstrate stack to a single substrate with effective isotropic properties by properly accounting for the in-plane and through-plane thermal conductivities, and the heat capacity. The estimates from the present model are validated with direct comparison to a finite volume numerical model for three-dimensional heat conduction. Case studies are presented to demonstrate the capabilities of the proposed network-based model and compare its estimates with the numerical conduction solution. In the presence of a step heat input, the results demonstrate that the model accurately captures the transient temperature rise across the multisubstrate stack comprising layers with different anisotropic properties. For a case where the rectangular stack is exposed to a sinusoidally varying heat input, the model is able to capture the general trends in the transient temperature fields in the plane where the heat source is applied to the multisubstrate stack. In summary, the developed resistance/capacitance network-based transient model offers a low-computational-cost method to predict the spatiotemporal temperature distribution over an arbitrary transient heat source interfacing with a multilayer stack of substrates.

Homoepitaxial GaN terahertz planar Schottky barrier diodes

In this work, a new type of terahertz Schottky barrier diode (SBD) based on homoepitaxial gallium nitride (GaN) was fabricated for high-power and high-frequency multiplier applications. The measured full width at half maximum of x-ray diffraction peaks for homoepitaxial GaN (002) and (102) plane is only one third of the heteroepitaxial GaN on sapphire substrate. Additionally, the increased electron mobility in both n−/n+ GaN epitaxial layers, induced by improved material quality, can effectively reduce the epitaxial resistance (R epi) and the spreading resistance. As a result, the total series resistance of the fabricated GaN SBD is 13.7 Ω, which is only 65% of that of heteroepitaxial GaN on a sapphire substrate. Additionally, the cut-off frequency (f c) is improved to 1.61 THz at zero bias voltage and the measured breakdown voltage is 16.17 V at −1 μA.

Performance improvement of heat sink with vapor chamber base and heat pipe

The heat sink with vapor chamber heat spreader has been the emerging design as it offers tremendous reduction in spreading resistance. However, this type of heat sinks suffer from the fin side temperature non-homogeneity, which hinders the heat transfer enhancement. The present study aimed to develop parallelogram fins integrated with heat pipes to increase the heat transfer performance of the heat sink with the vapor chamber heat spreader. The experimental and numerical investigations were performed on different heat sinks with different heat spreaders, including flat plate, vapor chamber, and vapor chamber combined with heat pipe. The air-cooled heat sink features a parallelogram fin configuration is proposed to tailor the temperature non-uniformity alongside the fins. The results showed that the overall thermal resistance of the heat sink with the vapor chamber and the vapor chamber combined with heat pipe spreader (no-cut fins) is about 50% and 55% lower than in the flat plate case. The proposed heat sink with vapor chamber combined with heat pipe spreader having a parallelogram fin structure offered about 61% reduction in thermal resistance and 45–50 °C reduction in chip temperature over the heat sink with flat plate heat spreader.

Introducing gallium in silicon and thin film polysilicon using self assembled monolayer doping

• Gallium compound synthesized to form Ga molecular monolayers on silicon surface. • Ga monolayer doping in silicon and thin film polysilicon demonstrated. • Junction depth of 200 nm with a dose 1.6*10 15 Ga atoms/cm 2 demonstrated in n -Si. • Near uniform doping in polysilicon films is achieved with 20% electrical activation. Monolayer Doping (MLD) is a technique involving the formation of a self-assembled dopant-containing layer on the substrate. The dopant is subsequently incorporated into the substrate by annealing, forming a diffused region. Following MLD, samples were capped with silicon dioxide and rapid thermal annealed (RTA). In this work, gallium doping using MLD has been demonstrated. Gallium containing compound Tris (2,4 pentanedionato) gallium(III) was synthesized, and shown to be suitable for monolayer doping silicon substrates and deposited thin film polysilicon. Secondary ion mass spectroscopy (SIMS) and spreading resistance probe (SRP) measurements were performed to determine the dopant profiles and dopant electrical activation. These results showed that a dose of 1.6*10 15 atoms/cm 2 was received, and the gallium dopant produced a 0.2 µm junction in n -type silicon. For polysilicon, the entire 0.4 μm film was evenly doped, with a concentration greater than 10 19 atoms/cm 3 throughout.

Bioinformatic analysis of the LCN2-SLC22A17-MMP9 network in cancer: The role of DNA methylation in the modulation of tumor microenvironment.

Several features of cancer cells such as proliferation, invasion, metastatic spreading, and drug resistance are affected by their interaction with several tumor microenvironment (TME) components, including neutrophil gelatinase-associated lipocalin (NGAL), solute carrier family 22 member 17 (SLC22A17), and matrix metallopeptidase 9 (MMP9). These molecules play a key role in tumor growth, invasion, and iron-dependent metabolism of cancer cells. However, the precise epigenetic mechanisms underlying the gene regulation of Lipocalin 2 (LCN2), SLC22A17, and MMP9 in cancer still remain unclear. To this purpose, computational analysis was performed on TCGA and GTEx datasets to evaluate the expression and DNA methylation status of LCN2, SLC22A17, and MMP9 genes in different tumor types. Correlation analysis between gene/isoforms expression and DNA methylation levels of LCN2, SLC22A17, and MMP9 was performed to investigate the role of DNA methylation in the modulation of these genes. Protein network analysis was carried out using reverse phase protein arrays (RPPA) data to identify protein–protein interactions of the LCN2–SLC22A17–MMP9 network. Furthermore, survival analysis was performed according to gene expression and DNA methylation levels. Our results demonstrated that LCN2 and MMP9 were mainly upregulated in most tumor types, whereas SLC22A17 was largely downregulated, representing a specific hallmark signature for all gastrointestinal tumors. Notably, the expression of LCN2, SLC22A17, and MMP9 genes was negatively affected by promoter methylation. Conversely, intragenic hypermethylation was associated with the overexpression of SLC22A17 and MMP9 genes. Protein network analysis highlighted the role of the LCN2–SLC22A17–MMP9 network in TME by the interaction with fibronectin 1 and claudin 7, especially in rectal tumors. Moreover, the impact of expression and methylation status of LCN2, SLC22A17, and MMP9 on overall survival and progression free interval was tumor type–dependent. Overall, our analyses provide a detailed overview of the expression and methylation status of LCN2, SLC22A17, and MMP9 in all TCGA tumors, indicating that the LCN2–SLC22A17–MMP9 network was strictly regulated by DNA methylation within TME. Our findings pave the way for the identification of novel DNA methylation hotspots with diagnostic and prognostic values and suitable for epi-drug targeting.

A theoretical study of thermal management of FBAR considering thickness- and temperature-dependent thermal conductivity of AlN

Reliable and long-term operation of thin film bulk acoustic resonators (FBARs) under high power relies on the optimization of thermal resistance. In this work, thermal design strategies for high power FBARs are explored theoretically. For accurate estimation of the thermal characteristics of FBARs, the thermal conductivity of the AlN epilayer with temperature and thickness dependence is included in the finite element simulation model, of which AlN thermal conductivity is calculated through normal-process, Umklapp, and boundary scattering. To further reduce thermal resistance and improve power capacity, the effects of aspect ratio, AlN thickness, the number of resonators, and pitch distance on thermal resistance are investigated. Compared with FBARs with a square electrode, the thermal resistance of the FBAR-on-diamond device is decreased by 43% at an aspect ratio of three. Meanwhile, the optimal AlN thickness is 2 µm, which maintains the balance between thermal resistance and electric performance. The power capacity is increased by 1.93 dB by substituting six resonators for four resonators. The improvement in power handling ability is attributed to the reduced thermal spreading resistance and lower power density. Our study can provide detailed thermal design strategies for high power FBARs toward high throughput data transmission.

An energy-efficient battery thermal management system incorporating a porous metal-based multiscale flow manifold

Development of an effective battery thermal management system (BTMS) is crucial for increasing the lifetime of electrochemical batteries and their reliable operation for various energy systems such as electric vehicles (EVs) and energy storage systems (ESSs). Liquid cooling can be a promising thermal management strategy for high energy density batteries due to its high heat transfer coefficient. However, conventional liquid cooling modules for large-scale battery packages require a high pumping power due to a long and serpentine flow path. They also induce a high-temperature deviation of battery cells since the coolant temperature gradually increases from inlet to outlet. Here, we introduce an energy-efficient liquid cooling module incorporating manifold flow distributors connected to a porous metal layer. The thermohydraulic performances of BTMS are investigated using both numerical and experimental platforms for the battery package composed of 24 pouch-type cells. The total energy capacity and heat generation of the package are determined to be ∼6.9 kWh and 504 W, respectively. The cooling module is designed to minimize the vortex generation within the cooling path, maximizing heat exchange area, and minimizing heat spreading resistance. The developed liquid cooling module shows ∼12.9 % higher temperature uniformity and 7.4 % lower maximum cell temperature compared to the straight channel-based module utilizing the same flow rate. The proposed liquid cooling strategy provides ∼43.3 °C of the maximum cell temperature with below 2 °C of temperature deviation by consuming only 3 L/min, which is ∼4.2 times lower flow rate compared to that of previously reported straight channel-based BTMS. This work will help develop energy-efficient electrochemical battery-based energy systems including EVs and ESSs.

Optimizing the heat source layout of chips using bionic method: Reduction of junction temperature

Optimizing the heat source layout to reduce the junction temperature is an important topic in the thermal design field of chips. However, the relationship between the heat source layout and the junction temperature is still ambiguous, and the optimization method suitable for actual chips is still rare, while it is quite desirable in engineering. In this work, we propose a feasible strategy to optimize the heat source layout using bionic method, and demonstrate the strategy by a flip chip ball grid array (FCBGA) case. The optimized layout can reduce the junction temperature and thermal spreading resistance by 2.38 K and 30.94%, respectively. The mechanism can be attributed to the heat dissipation advantage at the corner and edge positions of the heat source surface and the low temperature coupling between heat sources in the optimization process. This work illustrates a great promising potential of the bionic optimization method in the design of the CPU and GPU chips.

Unveiling the influence of selective-area-regrowth interfaces on local electronic properties of GaN p-n junctions for efficient power devices

We report correlated nanoscale mapping of the structure, composition, and properties of regrown GaN p-n junctions to identify how etching and non-planar regrowth processes limit diode performance via the introduction of unintentional dopants and defect states. p-GaN was selectively regrown in n-GaN trenches with SiO2 masks of variable mask-to-trench-width ratio. Dilute Al layers were periodically introduced during regrowth as markers of the growth interface. Correlated nanoscale mapping of doping, conductivity, and dopant complexes was achieved with atom probe tomography (APT), scanning spreading resistance microscopy (SSRM), and cathodoluminescence (CL) spectroscopy, respectively. The Al marker layers, detected by APT, enabled reconstruction of the faceted growth interface and correlation of the dopant concentration with position and time. The p-GaN growth rate is proportional to the mask-to-trench width ratio while the dopant incorporation rate is invariant. At trench edges, magnesium incorporation is suppressed, and oxygen incorporation enhanced, due to preferential incorporation on the semi-polar growth surface, leading to compensation and less abrupt p-n junctions; the SiO2 mask is a source of oxygen. Residual etch damage below the regrowth interface induces n-type and p-type conductivity, creating leakage pathways. The non-uniform Mg incorporation is driven by crystal anisotropy and is thus inherent to non-planar regrowth, but can be mitigated by engineering the regrowth interface and process parameters. The unprecedented integration of spatially resolved mapping of dopants, impurities, conductivity, and carrier type is a powerful approach to discriminating distinct factors that limit the performance of regrown diodes, enabling the rational optimization of process and device design.

Molecular Factors and Mechanisms Driving Multidrug Resistance in Uropathogenic Escherichia coli-An Update.

The rapid emergence of multidrug-resistant (MDR) bacteria indisputably constitutes a major global health problem. Pathogenic Escherichia coli are listed among the most critical group of bacteria that require fast development of new antibiotics and innovative treatment strategies. Among harmful extraintestinal Enterobacteriaceae strains, uropathogenic E. coli (UPEC) pose a significant health threat. UPEC are considered the major causative factor of urinary tract infection (UTI), the second-most commonly diagnosed infectious disease in humans worldwide. UTI treatment places a substantial financial burden on healthcare systems. Most importantly, the misuse of antibiotics during treatment has caused selection of strains with the ability to acquire MDR via miscellaneous mechanisms resulting in gaining resistance against many commonly prescribed antibiotics like ampicillin, gentamicin, cotrimoxazole and quinolones. Mobile genetic elements (MGEs) such as transposons, integrons and conjugative plasmids are the major drivers in spreading resistance genes in UPEC. The co-occurrence of various bacterial evasion strategies involving MGEs and the SOS stress response system requires further research and can potentially lead to the discovery of new, much-awaited therapeutic targets. Here, we analyzed and summarized recent discoveries regarding the role, mechanisms, and perspectives of MDR in the pathogenicity of UPEC.

Dopant Activation Depth Profiling for Highly Doped Si:P By Scanning Spreading Resistance Microscopy (SSRM) and Differential Hall Effect Metrology (DHEM)

Heavily n-doped epitaxially grown Si layers are of great importance for source/drain (S/D) application in advanced node nMOS devices. For contact resistivity reduction, the dopant activation level is very important. Various techniques are being used to evaluate dopant activation in Si:P layers. Among these two methods are Scanning Spreading Resistance Microscopy (SSRM) and Differential Hall Effect Metrology (DHEM). SSRM uses an atomic force microscope equipped with a hard conductive probe that is scanned in contact mode on the cross-sectioned sample’s surface and measures spreading resistance. Measured resistance values as a function of depth are converted into resistivity and carrier concentration depth profiles using calibration measurements and conversion relationships. DHEM provides depth profiles of mobility, resistivity and carrier concentration through a semiconductor layer by making successive sheet resistance (Rs) and Hall voltage measurements using Hall effect/Van der Pauw techniques, as the electrically active thickness of the layer is reduced through successive oxidation steps. Controlled oxidation is achieved by electrochemical anodization. Data collected can then be processed to yield the depth profiles. In this contribution we have carried out SSRM and DHEM measurements on Si:P epi layers subjected to different processing conditions including annealing and ohmic contact fabrication. Secondary Ion Mass Spectrometry (SIMS) was used to measure the total (active + inactive) dopant profiles through the films. Effects of these processes on dopant diffusion and activation were studied and the results from DHEM and SSRM were compared.In-situ phosphorus (P) doped Si epi-layers were grown over 300mm diameter boron doped monitor wafers. While one set was kept as the reference, a second set was treated by a spike-annealing process at 1000 °C. In a third set a Ti/TiN contact fabrication process was carried out and the contact was removed before analysis. In the fourth set contact process was applied to the spike annealed wafer before removal of the Ti/TiN layers. Bulk sheet resistance measurements were made using 4-point probe (4PP) for all the samples. SSRM measurements were carried out at IMEC. Cross-shaped Van der Pauw test-patterns were formed on 8mmx8mm areas on the samples and DHEM measurements were performed at ALP. Figure below shows the dopant depth profiles obtained by SIMS and the carrier concentration profiles from DHEM and SSRM techniques for samples D02 (as deposited Si:P) and D03 (spike annealed). One can make some general observations from the data in this figure. The total dopant concentration as measured by SIMS is ~ 1.4E21/cm3. There is only a small difference in the total dopant distribution profiles (SIMS) between the as deposited sample and the spike annealed sample. However, the spike annealed sample shows much higher dopant activation as measured by DHEM. Carrier concentration is ~2.5x higher in sample D03 (~5E20/cm3) compared to sample D02 (~2E20/cm3). Activation levels measured by SSRM, however, are lower for both samples, and the peak carrier concentration value increases only slightly upon spike annealing, going from ~2E20/cm3 in sample D02 to ~2.2E20/cm3 in sample D03. DHEM clearly indicates the sharp interface between the p-type substrate and the n-type epi-layer and its depth calibration agrees well with the expected thicknesses of the epi layers. The tail of the SSRM data is much more graded. Data from other samples will be presented and discussed in the final manuscript. Figure 1

Reduced graphene oxide films for reducing hotspot temperatures of electronic devices

The increase in the number of transistors in electronic circuits has increased the power density of electronic devices, which leads to the formation of hotspots on the microchips of the electronic devices. Hotspots deteriorate the lifespan and reliability of electronic devices. With the advantages of high thermal conductivity (κ), low cost, and feasibility for mass production, reduced graphene oxide (rGO) films have become a promising candidate for dispersing the excessive heat at the hotspots and alleviating the adverse effects caused by the hotspots. In this study, a chemical–thermal method combining the chemical reduction and thermal annealing process at a relatively low temperature of 1200 °C was utilized for the synthesis of rGO films. The synthesis method lowered the annealing temperature and yielded a high-quality rGO film. A high κ of 1653.9 ± 214.7 W/m-K was derived for the rGO film annealed at 1200 °C for 90 min. In addition, by bonding the rGO film on the Si chip, the hotspot temperature and thermal spreading resistance were reduced by 12 °C and 20%, respectively. The results indicate that the rGO films synthesized in this study retain a superior thermal property and can be employed for the thermal management of electronic devices.

Fruit Peel-Inspired Super-Stable Ionic Organohydrogel Electronics with Dense Hydrophobic Skin

Hydrogels are easily dehydrated during use and storage, making it difficult to maintain structural and performance stability, which greatly reduces their application value as wearable devices. Inspired by the structure of fruit, an ionic organohydrogel core containing Ca2+ and glycerol was first fabricated, and then, stearic acid (STA) was rivetted on the organohydrogel surface through (3-aminopropyl) triethoxysilane to obtain a dense hydrophobic coating (100 μm). The organohydrogel with hydrophobic skin presented better water spreading resistance and mechanical strength. In addition to the moisturizing effect of Ca2+ and glycerol, the skin also further blocks the contact between the organohydrogel and the air, thereby significantly enhancing the anti-dryness of the organohydrogel. Therefore, this organohydrogel has extremely outstanding structural, strength, and electrical conductivity stability. The developed strain sensor based on this organohydrogel can realize human motion monitoring capability at ultra-low temperature. This design idea, which combines multiple anti-drying mechanisms, has great expansion value for other gels suitable for various application scenarios.

Broadened Yu-Shiba-Rusinov states in dirty superconducting films and heterostructures

The interplay of a potential and magnetic disorder in superconductors has remained an active field of research for decades. Within the framework of the Usadel equation, we study the local density of states (LDOS) near a solitary classical magnetic impurity in a dirty superconducting film. We find that a potential disorder results in broadening of the $\ensuremath{\delta}$-function peak in the LDOS at the Yu-Shiba-Rusinov (YSR) energy. This broadening is proportional to the square root of a normal-state spreading resistance of the film. We demonstrate that modification of multiple scattering on the magnetic impurity due to intermediate scattering on surrounding potential disorder crucially affects a profile of the LDOS in the vicinity of the YSR energy. In addition, we find that a scanning-tunneling-microscopy tip can mask a YSR feature in the LDOS. Also, we study the LDOS near a chain of magnetic impurities situated in the normal region of a dirty superconductor/normal-metal junction. We find a resonance in the LDOS near the YSR energy. The energy scale of the resonant peak is controlled by the square root of the film resistance per square in the normal state.

Surface tailored graphite–polymer composite electrodes through cold plasma for electrochemical applications

AbstractComposite electrodes are gradually gaining interest due to their versatile applications. plastic chip electrode (PCE) comprising of graphite and Poly(methyl methacrylate) (PMMA) is one such composite that can be fabricated by simple solution‐phase mixing followed by solvent evaporation. In this study, we report more than two times enhancement in the bulk conductance of PCE by removing the passivating superficial polymer layer above the filler, through the treatment of cold plasma. Comparative characterization of the pre‐ and posttreated electrode has been performed by scanning electron microscopy (SEM), spreading resistance imaging (SRI), contact angle, and current–voltage characteristics as well as electrochemical impedance spectroscopy (EIS). Improved electroactivity of PCE has been demonstrated through cyclic voltammetry (CV).

Spectral Thermal Spreading Resistance of Wide-Bandgap Semiconductors in Ballistic-Diffusive Regime

To develop efficient thermal management strategies for wide-bandgap (WBG) semiconductor devices, it is essential to have a clear understanding of the heat transport process within the device and accurately predict the junction temperature. In this article, we use the phonon Monte Carlo (MC) method with the phonon dispersion of several typical WBG semiconductors, including GaN, SiC, AlN, and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\beta $ </tex-math></inline-formula> -Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , to investigate the thermal spreading resistance in a ballistic-diffusive regime. This work shows that when compared with Fourier’s law-based predictions, the increase in the thermal resistance caused by the ballistic effects is strongly related to the phonon dispersion. Based on the model derived under the gray-medium approximation and the results of dispersion MC, we obtained a thermal resistance model that can well address the issues of thermal spreading, ballistic effects, and the influence of phonon dispersion. The model can be easily coupled with finite-element method (FEM)-based thermal analysis and applied to different materials. This article can provide a clearer understanding of the influence of phonon dispersion on the thermal transport process, and it can be useful for the prediction of junction temperatures and the development of thermal management strategies for WBG semiconductor devices.

Dopant Activation Depth Profiling for Highly Doped Si:P By Scanning Spreading Resistance Microscopy (SSRM) and Differential Hall Effect Metrology (DHEM)

Heavily P-doped epitaxial Si layers were deposited over counter-doped Si substrates. P dopant activation was studied as a function of various processes used to prepare the samples. For electrical characterization, depth profiles of carrier concentration values were obtained using SSRM and DHEM techniques. Samples studied included an in-situ doped sample, a sample that was spike annealed at 1000ºC, a sample that was first coated with a Ti/TiN stack and then annealed for silicide formation before the Ti/TiN stack was removed, and a sample that was spike annealed + coated with Ti/TiN + annealed for silicide formation before the removal of the Ti/TiN stack. DHEM analysis showed substantial increase in dopant activation for spike annealed samples. SSRM results suggested lower carrier concentration values and more limited degree of activation. Formation of Ti/TiN contacts and its removal did not affect the carrier concentration values for the as-deposited epi layer. Sample that was first spike annealed and then subjected to contact formation process displaced a reduction in carrier concentration values as measured by DHEM.