John Y. W. Seto

Bio: John Y. W. Seto is an academic researcher from General Motors. The author has contributed to research in topics: Polycrystalline silicon & Silicon. The author has an hindex of 4, co-authored 4 publications receiving 2698 citations.

The electrical properties of polycrystalline silicon films

Abstract: Boron doses of 1×1012–5×1015/cm2 were implanted at 60 keV into 1‐μm‐thick polysilicon films. After annealing at 1100 °C for 30 min, Hall and resistivity measurements were made over a temperature range −50–250 °C. It was found that as a function of doping concentration, the Hall mobility showed a minimum at about 2×1018/cm3 doping. The electrical activation energy was found to be about half the energy gap value of single‐crystalline silicon for lightly doped samples and decreased to less than 0.025 eV at a doping of 1×1019/cm3. The carrier concentration was very small at doping levels below 5×1017/cm3 and increased rapidly as the doping concentration was increased. At 1×1019/cm3 doping, the carrier concentration was about 90% of the doping concentration. A grain‐boundary model including the trapping states was proposed. Carrier concentration and mobility as a function of doping concentration and the mobility and resistivity as a function of temperature were calculated from the model. The theoretical and ex...

Piezoresistive properties of polycrystalline silicon

Abstract: The piezoresistive gage factor of boron‐doped CVD polysilicon films deposited with a boron‐to‐silicon ratio of 2×10−4–1.2 ×10−2 on an aluminum‐oxide‐insulated molybdenum substrate is found to be between 15 and 27. Annealing increases the gage factor. The higher the doping, the lower is the gage factor. Over the range 20–140 °C, the gage factor is not temperature sensitive if the boron‐to‐silicon ratio is higher than 2×10−3 during deposition. The temperature dependence increases as the doping concentration is decreased. Our analysis shows that the piezoresistive properties in polysilicon is mainly due to the bulk crystallites.

Polycrystalline silicon pressure transducer

Abstract: A semiconductor pressure transducer having a polycrystalline silicon diaphragm providing an extremely pressure sensitive and temperature stable device, and a method of making the same. The polycrystalline silicon can easily be vapor deposited on an etch resistant layer covering a surface of a wafer or base, preferably monocrystalline silicon. Such vapor deposition of the polycrystalline silicon more accurately and consistently defines the thickness of the diaphragm than can be obtained by grinding or etching. A pressure responsive resistor formed in the diaphragm is automatically electrically isolated by the comparatively high resistivity of the polycrystalline silicon. Accordingly, PN junction isolation and passivating oxides on the diaphragm are not required thereby resulting in increased temperature stability.

Annealing characteristics of boron‐ and phosphorus‐implanted polycrystalline silicon

Abstract: Polycrystalline silicon films implanted with 1×1012 to 7.8×1015/cm2 doses of boron and phosphorus were isochronally annealed up to 1100 °C. Annealing below 600 °C removes the radiation damage created by the implantation process. For doses higher than 1×1014/cm2 an abrupt decrease in sheet resistance takes place between 650 and 700 °C. Hall measurements show that this decrease is the result of a large increase in both the carrier concentration and mobility. Electron‐reflection diffraction patterns show that recrystallization takes place within this temperature range. Annealing above 700 °C only causes a small further decrease in the sheet resistance.

Bulk nanostructured thermoelectric materials: current research and future prospects

Abstract: Thermoelectrics have long been recognized as a potentially transformative energy conversion technology due to their ability to convert heat directly into electricity. Despite this potential, thermoelectric devices are not in common use because of their low efficiency, and today they are only used in niche markets where reliability and simplicity are more important than performance. However, the ability to create nanostructured thermoelectric materials has led to remarkable progress in enhancing thermoelectric properties, making it plausible that thermoelectrics could start being used in new settings in the near future. Of the various types of nanostructured materials, bulk nanostructured materials have shown the most promise for commercial use because, unlike many other nanostructured materials, they can be fabricated in large quantities and in a form that is compatible with existing thermoelectric device configurations. The first generation of these materials is currently being developed for commercialization, but creating the second generation will require a fundamental understanding of carrier transport in these complex materials which is presently lacking. In this review we introduce the principles and present status of bulk nanostructured materials, then describe some of the unanswered questions about carrier transport and how current research is addressing these questions. Finally, we discuss several research directions which could lead to the next generation of bulk nanostructured materials.

Defects in perovskite-halides and their effects in solar cells

Abstract: Solar cells based on perovskite-halide light absorbers have a unique set of characteristics that could help alleviate the global dependence on fossil fuels for energy generation They efficiently convert sunlight into electricity using Earth-abundant raw materials processed from solution at low temperature Thus, they offer potential for cost reductions compared with or in combination with other photovoltaic technologies Nevertheless, to fully exploit the potential of perovskite-halides, several important challenges must be overcome Given the nature of the materials — relatively soft ionic solids — one of these challenges is the understanding and control of their defect structures Currently, such understanding is limited, restricting the power conversion efficiencies of these solar cells from reaching their thermodynamic limit This Review describes the state of the art in the understanding of the origin and nature of defects in perovskite-halides and their impact on carrier recombination, charge-transport, band alignment, and electrical instability, and provides a perspective on how to make further progress Understanding of defect physics in perovskite-halide semiconductors is essential to control the effects of structural and chemical defects on the performance of perovskite solar cells Petrozza and Ball review the current knowledge of defects in these materials

Review: Semiconductor Piezoresistance for Microsystems

Abstract: Piezoresistive sensors are among the earliest micromachined silicon devices. The need for smaller, less expensive, higher performance sensors helped drive early micromachining technology, a precursor to microsystems or microelectromechanical systems (MEMS). The effect of stress on doped silicon and germanium has been known since the work of Smith at Bell Laboratories in 1954. Since then, researchers have extensively reported on microscale, piezoresistive strain gauges, pressure sensors, accelerometers, and cantilever force/displacement sensors, including many commercially successful devices. In this paper, we review the history of piezoresistance, its physics and related fabrication techniques. We also discuss electrical noise in piezoresistors, device examples and design considerations, and alternative materials. This paper provides a comprehensive overview of integrated piezoresistor technology with an introduction to the physics of piezoresistivity, process and material selection and design guidance useful to researchers and device engineers.

High-k organic, inorganic, and hybrid dielectrics for low-voltage organic field-effect transistors.

Abstract: 2.2. Interface Trapping Effects 211 3. High-k Dielectric Materials for OFETs 212 3.1. Inorganic Dielectrics 212 3.1.1. Aluminum Oxide 213 3.1.2. Tantalum Oxide 215 3.1.3. Titanium Dioxide 216 3.1.4. Hafnium Dioxide 217 3.1.5. Zirconium Dioxide 218 3.1.6. Cerium Dioxide 218 3.2. Organic Dielectrics 218 3.2.1. Polymer Dielectrics 218 3.2.2. Self-Assembled Monoand Multilayers 225 3.3. Hybrid Dielectrics 227 3.3.1. Polymeric-Nanoparticle Composites 227 3.3.2. Inorganic-Organic Bilayers 232 3.3.3. Hybrid Solid Polymer Electrolytes 235 4. Summary 235 5. Acknowledgments 236 6. References 236