EXTRINSIC SEMICONDUCTORS PDF

The semiconductor is divided into two types. One is Intrinsic Semiconductor and other is Extrinsic semiconductor. An extremely pure. Semiconductor materials can be classified into two types viz., Intrinsic Semiconductors and Extrinsic Semiconductors. Semiconductors in their. Lecture 6: Extrinsic semiconductors. Contents. 1 Introduction. 1. 2 n-type doping. 2. 3 p-type doping. 4. 4 Conductivity in extrinsic Si. 7. 5 Compensation doping.


EXTRINSIC SEMICONDUCTORS PDF

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EXTRINSIC SEMICONDUCTORS PDF


Extrinsic semiconductor - P-type semiconductor

Therefore, all the trivalent impurities are called extrinsic semiconductors. A small addition of impurity boron provides millions of holes. Charge on p-type semiconductor So many people think that p-type semiconductor has large number of holes and current conduction is mainly due to these holes.

So, the total electric charge of p-type semiconductor is positive. Excess holes increase the hole carrier concentration p0 of the semiconductor, creating a p-type semiconductor. Semiconductors and dopant atoms are defined by the column of the periodic table in which they fall. The column definition of the semiconductor determines how many valence electrons its atoms have and whether dopant atoms act as extrinsic semiconductors semiconductor's donors or acceptors.

EXTRINSIC SEMICONDUCTORS PDF

Conversely, when a group IV atom replaces the group V element, the extrinsic semiconductors IV atom acts as an acceptor.

Moreover, it is to be noted that, extrinsic semiconductors an electron moves into the hole to recombine, it leaves a new hole in its previous place which in turn will be filled by some other electron.

Intrinsic Semiconductor and Extrinsic Semiconductor

This indicates that the movement of electrons in one direction can be viewed as the movement of holes in the opposite direction. Extrinsic semiconductors, such a semiconductor material becomes conductive in nature. However, it is to be noted that, for this case, the total number of holes will be equal to the sum of the holes induced due to doping and the holes generated due to the thermal excitation extrinsic semiconductors, unlike the electrons which are produced only due to the process of thermal excitation.

EXTRINSIC SEMICONDUCTORS PDF

The number of free electrons and holes in extrinsic semiconductor are not equal. Types of impurities Two types of impurities extrinsic semiconductors added to the semiconductor.

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They are pentavalent and trivalent impurities. Pentavalent impurities Pentavalent impurity atoms have 5 valence electrons. For extrinsic semiconductors, the dopant density is always extrinsic semiconductors higher than the intrinsic carrier density: In the case of a p-type material, the hole density is then close to the dopant extrinsic semiconductors NA.

Since the law of mass action is always true, we obtain the following expressions for the extrinsic semiconductors densities The Fermi level for a p-type semiconductor or chemical potential is then:



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