Tag: solid state

$Tl _2Ca _2Ba _2Cu _3O _{10}$ possess superconductivity at 125 K.

Superconductors have applications in electronics, building magnets, aviation, transportation (trains which move in air without rails) and power transmission.

The n-type semiconductors are obtained when $Si$ or $Ge$ are doped with elements of group 15, eg, Arsenic $(As)$, while p-type semiconductors are obtained when $Si$ or $Ge$ are doped with traces of group 13 , ie Indium $(In)$ , Boron $(B)$.

An extrinsic semiconductor is one that has been doped; during manufacture of the semiconductor crystal a trace element or chemical called a doping agent has been incorporated chemically into the crystal, for the purpose of giving it different electrical properties than the pure semiconductor crystal.

$p-$type semiconductors have a larger hole concentration than electron concentration. In p-type semiconductors, holes are the majority carriers and electrons are the minority carriers. $p-$type semiconductors are created by doping an intrinsic semiconductor with acceptor impurities. A common $p-$type dopant for silicon is boron or gallium. There will be no charge on the semiconductor.

$TiO _{ 3 }$ behaves as conductor or insulator depending on temperature because of variation of energy gap between valence band and conduction band with the variation of temperature.

An $n-$type semiconductor is made by adding a small amount of a Group-V element such as phosphorous ($P$) or arsenic ($As$) to the intrinsic semiconductor. Group-V elements have five valence electrons per atom.

The conductance through electrons is called n-type conduction and if through positive semiholes, it is called p-type conduction.
Doping involves preparation of semi-conductors by the presence of impurities in the intrinsic semiconductor.With donor impurities, we get n-type semi-conductors and with acceptor impurities, we get p-type semi-conductors.

The addition of small amount of foreign impurity in the host crystal is called as doping. It results in an increase in the electrical conductivity of the crystal. Doping of group 14 elements (such as Si, Ge etc.) with elements of group 15 (such as As) produces an excess of electrons in the crystals and thus, gives n-type semiconductors. Doping of groups 14 elements with group 13 elements (such as Indium) produces holes (electron deficiency) in the crystals. Thus, p-type semiconductors are produced. The symbol 'p' indicates flow of positive charge. Also, the band gap in germanium is small as Ge is a semi-conductor.

The addition of a small amount of foreign impurity in the host crystal is called doping.