Review on thermal energy storage with phase change: materials, heat transfer analysis and applications

Light-Emitting Diodes. (Monographs in Electrical and Electronic Engineering.) By A. A. Bergh and P. J. Dean. Pp. viii+591. (Clarendon: Oxford; Oxford University: London, 1976.) £22.

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Light-emitting diodes

Gallium oxide (Ga2O3) is emerging as a viable candidate for certain classes of power electronics, solar blind UV photodetectors, solar cells, and sensors with capabilities beyond existing technologies due to its large bandgap. It is usually reported that there are five different polymorphs of Ga2O3, namely, the monoclinic (β-Ga2O3), rhombohedral (α), defective spinel (γ), cubic (δ), or orthorhombic (e) structures. Of these, the β-polymorph is the stable form under normal conditions and has been the most widely studied and utilized. Since melt growth techniques can be used to grow bulk crystals of β-GaO3, the cost of producing larger area, uniform substrates is potentially lower compared to the vapor growth techniques used to manufacture bulk crystals of GaN and SiC. The performance of technologically important high voltage rectifiers and enhancement-mode Metal-Oxide Field Effect Transistors benefit from the larger critical electric field of β-Ga2O3 relative to either SiC or GaN. However, the absence of clear demonstrations of p-type doping in Ga2O3, which may be a fundamental issue resulting from the band structure, makes it very difficult to simultaneously achieve low turn-on voltages and ultra-high breakdown. The purpose of this review is to summarize recent advances in the growth, processing, and device performance of the most widely studied polymorph, β-Ga2O3. The role of defects and impurities on the transport and optical properties of bulk, epitaxial, and nanostructures material, the difficulty in p-type doping, and the development of processing techniques like etching, contact formation, dielectrics for gate formation, and passivation are discussed. Areas where continued development is needed to fully exploit the properties of Ga2O3 are identified.

A review of Ga2O3 materials, processing, and devices

International Technology Roadmap for Semiconductors 2003の要求清浄度について － シリコンウエハ表面と雰囲気環境に要求される清浄度, 分析方法の現状について －

Small, light weight and multifunctional electronic components are attracting much attention because of the rapid growth of the wireless communication systems and microwave products in the consumer electronic market. The component manufacturers are thus forced to search for new advanced integration, packaging and interconnection technologies. One solution is the low temperature cofired ceramic (LTCC) technology enabling fabrication of three-dimensional ceramic modules with low dielectric loss and embedded silver electrodes. During the past 15 years, a large number of new dielectric LTCCs for high frequency applications have been developed. About 1000 papers were published and ∼500 patents were filed in the area of LTCC and related technologies. However, the data of these several very useful materials are scattered. The main purpose of this review is to bring the data and science of these materials together, which will be of immense help to researchers and technologists all over the world. The comme...

Low loss dielectric materials for LTCC applications: a review

A finite element analysis approach is developed and used to efficiently evaluate and optimize the boiling performance of longitudinal rectangular plate fin heat sinks, including the explicit dependence of fin spacing on boiling heat transfer coefficients and on the critical heat flux (CHF). Polished silicon heat sinks are shown to dissipate at nearly five times the CHF limit of the unfinned base area and outperform comparable aluminum heat sinks by a factor of 2. For optimum heat sink geometries, over the parameter ranges explored, the fin thickness is found to be approximately equal to the fin spacing, and the relationship between the optimum thickness and spacing is demonstrated to be relatively insensitive to the fin thermal conductivity. Results suggest that even greater performance enhancements may be gained with appropriately-selected advanced materials.

Optimization of Pool Boiling Heat Sinks Including the Effects of Confinement in the Interfin Spaces

The thermal isolation capabilities of fluid cooled via-enhanced glass interposers are investigated with resistive-heater test chips and IR thermography. Previous studies have shown that the degree of thermal coupling between adjacent devices hosted on via-enhanced low conductivity interposers is lower than those on silicon interposers, but at the cost of increased chip-to-ambient thermal resistance. By integrating the enhanced low-k interposer with an embedded microgap cooler, much higher chip power can be dissipated while maintaining an acceptable temperature rise.

Reducing thermal coupling using fluid cooled low-k interposers

Estimation of major correlations for frictional pressure drop in gas-liquid two-phase flow in horizontal pipes using predicted flow regime information

On-chip hotspot thermal management with an embedded array of silicon thermoelectric microcoolers

A series of single-phase water microgap cooling experiments (gap height: 200 μm) are conducted on via arrays in 400 μm thick glass interposers. Surface temperature rise is compared to trials run with bulk Si of the same thickness. The results show that the copper vias are necessary to control the temperature rise of the glass substrate, and that while the via-enhanced interposers do exhibit a larger thermal resistance than silicon, they also provide the desired increase in lateral thermal isolation. As flow rates within the gap are increased (approaching Re=1600), the penalty associated with constraining the flow of heat to the footprint of the via array is mitigated, owing to the reduction in the thermal resistance attributable to the convection boundary.

Avram Bar-Cohen

Papers

Optimization of Pool Boiling Heat Sinks Including the Effects of Confinement in the Interfin Spaces

Reducing thermal coupling using fluid cooled low-k interposers

Estimation of major correlations for frictional pressure drop in gas-liquid two-phase flow in horizontal pipes using predicted flow regime information

On-chip hotspot thermal management with an embedded array of silicon thermoelectric microcoolers

Microgap cooling of via-enhanced glass interposers