ECE 331: Introduction to Materials for Electrical Engineers Course Objective... Introduce fundamental concepts in Materials Science and how they are used in ECE You will learn about: material structure how structure dictates properties how electronic & physical properties are related This course will help you to: use materials properly realize new design opportunities with materials understand the physics of semiconductor devices
ECE 331 Intro to Materials for ECE Materials in ECE are: semiconductors, metals (e.g. Al contacts), t polymers (e.g. encapsulants for LEDs) and insulators (ceramics such as silicon dioxide in FETs) Materials in ECE are single crystals, polycrystals, amorphous layers and nanostructures t Si (silicon) is NOT the only semiconductor (though Si electronics is the world s largest manufacturing industry), but it is the most important one and will remain so!
ECE 331 Intro to Materials for ECE III-V examples GaAs InP InAs AlGaAs InGaAs InGaAsP GaN InGaN Know your periodic table! Find your old chemistry notes! III -V
Materials Roadmap for Device Technologies: the Bandgap vs Lattice Constant Relationship III-V electronics CD Lasers Fiber pump lasers Space solar ECE applications are expanding across this entire space! CMOS, BiCMOS, Terrestrial solar, Power CMOS Telecomm Optoelectronics thermophotovoltaics
TECHNOLOGY ROADMAPS: New Age for ECE Materials and opportunities Roadmaps are calling for unusual properties not obtainable using conventional materials or processes Electronics: - Nanoscale patterning - optical interconnects - speed enhancing materials Optoelectronics: - tunable light emission/detection wavelengths - seamless integration with electronic systems Alternative Energy: - clean, renewable, cheap, safe, autonomous - Biocompatiblity and medicine
The Materials Selection Process 1. Pick Application Determine required Properties Properties: mechanical, electrical, thermal, magnetic, optical, deteriorative. 2. Properties Identify candidate Material(s) Material: structure, composition. 3. Material Identify required Processing Processing: changes structure and overall shape ex: casting, sintering, vapor deposition, doping forming, joining, annealing.
ELECTRICAL Electrical Resistivity of Copper: y, r m) esistivit 0-8 Ohm- Re (10 6 Adapted from Fig. 18.8, Callister 7e. (Fig. 18.8 adapted from: J.O. Linde, 5 Ann Physik 5, 219 (1932); and C.A. Wert and R.M. Thomson, Physics of Solids, 2nd edition, 4 McGraw-Hill Company, New York, 1970.) 3 2 1 0-200 -100 0 T ( C) Adding impurity atoms to Cu increases resistivity. Deforming Cu increases resistivity.
THERMAL Space Shuttle Tiles: --Silica fiber insulation offers low heat conduction. Thermal Conductivity of Copper: - decreases when you add zinc! 100mm Adapted from chapteropening photograph, Chapter 19, Callister 7e. (Courtesy of Lockheed Missiles and Space Company, Inc.) Adapted from Fig. 19.4W, Callister 6e. (Courtesy of Lockheed Aerospace Ceramics Systems, Sunnyvale, CA) (Note: "W" denotes fig. is on CD-ROM.) Th hermal Co onductivi ity (W/ /m-k) 400 300 200 100 0 0 10 20 30 40 Composition (wt% Zinc) Adapted from Fig. 19.4, Callister 7e. (Fig. 19.4 is adapted from Metals Handbook: Properties and Selection: Nonferrous alloys and Pure Metals, Vol. 2, 9th ed., H. Baker, (Managing Editor), American Society for Metals, 1979, p. 315.)
MAGNETIC Magnetic Storage: --Recording medium is magnetized by recording head. Magnetic Permeability vs. Composition: --Adding 3 atomic % Si makes Fe a better recording medium! Fig. 20.23, Callister 7e. (Fig. 20.2323 is from J.U. Lemke, MRS Bulletin, Vol. XV, No. 3, p. 31, 1990.) Magnetiz zation Fe+3%Si Fe Magnetic Field Adapted from C.R. Barrett, W.D. Nix, and A.S. Tetelman, The Principles of Engineering Materials, Fig. 1-7(a), p. 9, 1973. Electronically reproduced by permission of Pearson Education, Inc., Upper Saddle River, New Jersey.
OPTICAL Transmittance: --Aluminum oxide may be transparent, translucent, or opaque depending on the material structure. polycrystal: polycrystal: single crystal low porosity high porosity Adapted from Fig. 1.2, Callister 7e. (Specimen preparation, P.A. Lessing; photo by S. Tanner.)
Photovoltaics and the role of materials
Conversion of radiant heat to electricity: Thermophotovoltaics Front Contact Grid Finger Interconnect n InPAs window n/p InGaAs Emitter/Bas e p InPAs BSF p/n InGaAs TJ n InPAs Buffer Semi-Insulating InP SiN/Gold Back Surface Reflector SEM Micrograph Of Processed Ternary MIM Structure Efficiency ~18% With addition of a a front surface filter 0.9 W/cm 2 power density - h = 20.6% at a radiator temperature re of 1058 C. System Eff ficiency (%) 23 22 21 20 19 18 17 16 15 25.6 C 25.6 C 26.7 C 26.7 C 850 900 950 1000 1050 1100 Radiator Temperature ( C)
Wide Bandgap Semiconductors GaN: Energy-Efficient Solid State Lighting g (SSL) Al-Ga-In-N spans uv-blue-green-red-near ir spectrum National SSL Initiative: by 2020: 50% of elec.used by lighting: save $115B eliminate 258M metric ton of C emission
Course Goals: SUMMARY Use the right material for the job. Understand the relation between properties, structure, and processing. Recognize new design opportunities offered by materials selection. Appreciate the relationship between devices, their characteristics and their constituent materials