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Presentation on Semiconductor Fundamental Submitted by : MD. Jubayer Ahmed MD. Mehedi Hasan Tanvir Anjum A.S. Shakur Submitted to: Mohiuddin Munna Lecture Dept. of EEE SUST, Sylhet. Shahjalal University of Science & Technology, Sylhet. Dept. of Electrical & Electronic Engineering. 2010338025 2010338019 2010338007 2010338013

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Structure : The atomic arrangement within a solid can be classified as follows Amorphous Polycrystalline Crystalline

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Amorphous: An Amorphous solid is a material in which there is no recognizable long-range order in positioning of atoms within the material. Crystalline: A crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an ordered pattern extending in all three spatial dimensions.

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Polycrystalline: Polycrystalline materials are solids that are composed of many crystallites of varying size and orientation.

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Unit cell Unit cell: The unit cell is a small box containing one or more atoms arranged in 3-dimensions

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The unit cell is represented in terms of its lattice parameters.

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On the cubic category there are three types of unit cells Simple cubic Body-centered cubic Face-centered cubic

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Silicon Lattices In Si (and Ge) the lattice structure is diamond lattice. Diamond Lattice: 1.Similar to F.C.C but have four additional atoms. 2.Most of the iii-v semiconductors are diamond lattice. 3.Diamond lattice similar to zincblende structure.

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Fig: silicon lattice

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Fig: Diamond LatticeFig: Zincblende Structure

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MILLER INDICES The position of the planes or the direction of a vector in the lattice are usually described by three integers.

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HOW TO FIND MILLER INDICES. Determine the intercepts of the plane intersecting the xyz coordinate.a1 – x direction, a2 – y direction, and a3 – z direction. Take the reciprocals of the intercepts. h = 1/a1, l = 1/a2, and m = 1/a3. Reduce the result to the smallest integer. ( hkl) – for single plane and {hkl} for a group of planes. Negative Miller values are denoted by a bar on top. Example - (ħkl). Planes without an intersecting intercept are taken as infinite planes (∞).

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Obtaining Ultrapure Si: In nature Si is found in a various forms of silicon dioxide or silicates. silicon the second most abundant element in the Earth's crust (about 28% by mass) after oxygen. Czochralski process.

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