ntype semiconductors can be formed by addition of the elemen

n-type semiconductors can be formed by addition of the elemental metals to the parent compound. For example, addition of Zr to ZrO or Ti to TiO. Like wise, p-type semiconductors can be formed by increasing the amount of the nonmetal In Cu2S (add S), Cul (add elemental I), or ZnO (add O). Explain how this is possible.

Solution

N-Type semiconductor is created by adding pentavalent impurities like Phosphorus (P), Arsenic (As), or Antimony (Sb). The purpose of doing so is to make more charge carriers, or electronsavailable in the material for conduction.........

Semiconductor materials like Silicon and Germanium have four electrons in their outer shell (valence shell). All the four electrons are used by the semiconductor atom in forming bonds with its neighboring atoms, leaving a low number of electrons available for conduction. Pentavalent elements are those elements which have five electrons in their outer shell. When pentavalent impurities like Phosphorus or Arsenic are added into semiconductor, four electrons form bonds with the surrounding silicon atoms leaving one electron free. The resulting material has a large number of free electrons. Since electrons are negative charge carriers, the resultant material is called N-type (or negative type) semiconductor. The pentavalent impurity that is added is called \'Dopant\' and the process of addition is called \'doping\'.////////

N-Type semiconductor is manufactured by doping \'intrinsic\' or pure semiconductor material. The amount of impurity added is very small compared to the amount of semiconductor. Characteristics and nature of the resultant semiconductor can be controlled by controlling the quantity of \'dopant\'.


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The materials chosen as suitable dopants depend on the atomic properties of both the dopant and the material to be doped. In general, dopants that produce the desired controlled changes are classified as either electron acceptors or donors. Semiconductors doped with donor impurities are called n-type, while those doped with acceptor impurities are known as p-type. The n and p type designations indicate which charge carrier acts as the material\'s majority carrier. The opposite carrier is called the minority carrier, which exists due to thermal excitation at a much lower concentration compared to the majority carrier.

For example, the pure semiconductor silicon has four valence electrons which bond each silicon atom to its neighbors. In silicon, the most common dopants are group III and group V elements. Group III elements all contain three valence electrons, causing them to function as acceptors when used to dope silicon. When an acceptor atom replaces a silicon atom in the crystal, a vacant state ( an electron \"hole\") is created, which can move around the lattice and functions as a charge carrier. Group V elements have five valence electrons, which allows them to act as a donor; substitution of these atoms for silicon creates an extra free electron. Therefore, a silicon crystal doped with boron creates a p-type semiconductor whereas one doped with phosphorus results in an n-type material.