Extrinsic Semiconductor Conductivity with Temperature
Conduction of current in the intrinsic semiconductor is poor at normal room temperature, the extrinsic semiconductor can do so.Then, the n-type semiconductor is not useful and inapplicable for electronics device apps technology.Then, very much required to add a small amount of impurity to the intrinsic semiconductor for increasing current conduction capability. Then, the semiconductor becomes applicable to apply for electronics technology as well as an impure or extrinsic semiconductor.This method and process of adding impurity are defined as doping in physics.
Extrinsic Semiconductors are two types: a) N-type semiconductor b) P-type semiconductor.
The n-type Extrinsic Semiconductor definition:
If a few pentavalent impurities (arsenic, antimony & phosphorus) is added to the intrinsic pure semiconductor (germanium or silicon crystal) then, pure semiconductor becomes N-type semiconductor (impure) extrinsic semiconductor.
Since above image of n-type extrinsic semiconductor, Phosphorus pentavalent impurity atom is added to the germanium crystal.Germanium atom has four valence electrons in its outermost shell and Phosphorus has five valence electrons in its outermost shell. Each phosphorus atom formed a covalent bond with surrounding four germanium atoms.Thus, four valence electrons of phosphorus atom form a covalent bond with four valence electrons of individual germanium atoms. The fifth valence electron is poorly bounded with phosphorus atom, a Fifth valence electron is a free electron. Under the influence of applied electric field or thermal energy free electron become excited and move towards conduction band from valence band. Pentavalent impurities are to be said donor impurities because it donates one electron for conduction of current. Here, the addition of pentavalent impurities (phosphorus) increases the number of electrons or electron concentration in the conduction band, hence current conductivity is increased for –ve charge electrons, –ve charge electrons are majority carrier and holes (+ve charged) are minority carrier.So, its to be said n-type semiconductor definition.
The p-type Extrinsic Semiconductor diagram:
If a small amount of trivalent impurity (boron, aluminum, gallium, indium, and bismuth) is added to the intrinsic pure semiconductor (germanium or silicon crystal) the pure semiconductor becomes P-type semiconductor (impure) extrinsic semiconductor.
Since above image p-type extrinsic semiconductor, gallium (Ga )trivalent impurity atom is added to germanium crystal.Germanium atom has four valence electrons in its outermost shell and gallium (Ga ) atom has three valence electrons in its outermost shell. A gallium (Ga ) atom form covalent bond with surrounding four Germanium atoms. Another Germanium (Ge) atom & gallium (Ga ) atom form one covalent bond is not a complete due shortage of an electron, which generates a hole. The hole is to be said +ve charge carrier. Thus, by trivalent impurity gallium (Ga ) generates a large number of holes in the valence band. Current conductivity is increased due to generates large numbers of +ve charged holes in a P-type semiconductor.Trivalent impurities such as gallium (Ga ) is called acceptor impurity because it accepts free electrons in the place of holes for electrical current conduction.
where numbers of +ve charge carrier hole much greater than numbers of negative charge carrier free electrons.Current flowing is increased for +ve charge carrier holes. So, it to be said P-type semiconductor. Above article are p and n-type semiconductor definition in details.This is a way of p-type semiconductor formation as well as the difference between n-type and p-type semiconductor.
Since the graph, intrinsic vs extrinsic semiconductor OR difference between the intrinsic and extrinsic semiconductor:-
In case of an intrinsic semiconductor silicon, minimum 300 Kelvin temperature required to increase the number of electrons or more electrons concentration as well as increase electrical conductivity. Mean, the intrinsic carrier concentration of silicon at 300k.
In case of an extrinsic semiconductor, very low amount thermal energy required to increase the number of electrons or electrons concentration as well as increase the electric current conduction. Hence, the extrinsic impure semiconductor has much more convenience and effectiveness.