N-type semiconductor

An N-type semiconductor (N for Negative) is a material obtained by carrying out a process of doping, that is, by adding some amount of an element with more electrons to a semiconductor element with fewer electrons, in order to increase the number of free charge carriers. In this case the charge carriers are negatively-charged, hence "N-type". The impurity is called a "donor material," because it gives away (donates) weakly-bound outer electrons to the semiconductor atoms. The resulting impure crystal compound has useful conduction characteristics.

The purpose of N-type doping is to produce an abundance of mobile or "carrier" electrons in the material. To help understand how N-type doping is accomplished, consider the case of silicon (Si). Si atoms have four valence electrons, each of which is covalently bonded with each of the four adjacent Si atoms. If an atom with five valence electrons, such as those from group 15 (old group VA, a.k.a. nitrogen group) of the periodic table (eg. phosphorus (P), arsenic (As), or antimony (Sb)), is incorporated into the crystal lattice in place of a Si atom, then that atom will have four covalent bonds and one unbonded electron. This extra electron is only weakly bound to the atom and can easily be excited into the conduction band. At normal temperatures, virtually all such electrons are excited into the conduction band. Since excitation of these electrons does not result in the formation of a hole, the number of electrons in such a material far exceeds the number of holes. In this case the electrons are the majority carriers and the holes are the minority carriers. Because the five-electron atoms have an extra electron to "donate", they are called donor atoms. Note that each movable electron within the semiconductor is never far from an immobile positive dopant ion, and the N-doped material normally has a net electric charge of zero.

To a first approximation, a sufficiently doped N-type semiconductor can be thought of as only conducting electrons.

In an N-type semiconductor, the fermi level lies closer to the conduction band edge.

See also

semiconductor
Donor (semiconductors)
P-type semiconductor
I-type semiconductor
Transistor
p-n-p transistor
n-p-n transistor

Translation of "N-type semiconductor"

Arabic: شبه موصل سالب, Spanish: Semiconductor#Semiconductor tipo N, French: Semi-conducteur#Dopage de type N, Korean: N형 반도체, Japanese: N型半導体, Russian: Полупроводник n-типа, Ukrainian: Напівпровідник n-типу.