Presentation on Semiconductor Fundamental

Submitted by :MD. Jubayer AhmedMD. Mehedi HasanTanvir AnjumA.S. Shakur

Submitted to:Mohiuddin MunnaLectureDept. of EEESUST, Sylhet.

Shahjalal University of Science & Technology, Sylhet.Dept. of Electrical & Electronic Engineering.

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

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.

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

Unit cell Unit cell:

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

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

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

Silicon LatticesIn 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.

Fig: silicon lattice

Fig: Diamond Lattice Fig: Zincblende Structure

MILLER INDICES The position of the planes or the direction of a vector in the

lattice are usually described by three integers.

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 (∞).

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.

Thank You