Semiconductors and Doping

en · official · sha256:ad71d83ee4824c2372908ce65b57ac506e686ad22a566121dff179016de4703a

<definition id="fs-id1172100950511"> <term>acceptor impurity</term> <meaning id="fs-id1172098591331">atom substituted for another in a semiconductor that results in a free electron</meaning> </definition>

en · official · sha256:dd486d4966307fb6f70d81a78aee381e744d8db3565cf5baa726329f66d02eb7

<para id="fs-id1172098618759">Doping can also be accomplished using impurity atoms that typically have one <emphasis effect="italics">fewer</emphasis> valence electron than the semiconductor atoms. For example, Al, which has three valence electrons, can be substituted for Si, as shown in <link target-id="CNX_UPhysics_42_06_Impurities"/>(b). Such an impurity is known as an <term id="term-00007">acceptor impurity</term>, and the doped semiconductor is called a <term id="term-00008"><emphasis effect="italics">p</emphasis>-type semiconductor</term>, because the primary carriers of charge (holes) are positive. If a hole is treated as a positive particle weakly bound to the impurity site, then an empty electron state is created in the band gap just above the valence band. When this state is filled by an electron thermally excited from the valence band (<link target-id="CNX_UPhysics_42_06_Excited"/>(a)), a mobile hole is created in the valence band. By adding more acceptor impurities, we can create an impurity band, as shown in <link target-id="CNX_UPhysics_42_06_Excited"/>(b).</para>

Referencing norms: AcceptorDopedIsNotNType, AcceptorImpurityGivesPType, doped_with_acceptor_impurity

en · official · sha256:2bee1d20715ffd9fe26986f694b5a9742af8c1104518aef87a875927c7a18630

<definition id="fs-id1172098464068"> <term>donor impurity</term> <meaning id="fs-id1172098694815">atom substituted for another in a semiconductor that results in a free electron hole</meaning> </definition>

en · official · sha256:2ba96f91329852017b06a61c8850c8c2bd5befbea8eedc3a4bb36f3cc1f0ba14

<para id="fs-id1172100991668">Arsenic has five valence electrons, whereas silicon has only four. This extra electron must therefore go into the conduction band, since there is no room in the valence band. The arsenic ion left behind has a net positive charge that weakly binds the delocalized electron. The binding is weak because the surrounding atomic lattice shields the ion’s electric field. As a result, the binding energy of the extra electron is only about 0.02 eV. In other words, the energy level of the impurity electron is in the band gap below the conduction band by 0.02 eV, a much smaller value than the energy of the gap, 1.14 eV. At room temperature, this impurity electron is easily excited into the conduction band and therefore contributes to the conductivity (<link target-id="CNX_UPhysics_42_06_ExtraElect"/>(a)). An impurity with an extra electron is known as a <term id="term-00004">donor impurity</term>, and the doped semiconductor is called an <term id="term-00005"><emphasis effect="italics">n</emphasis>-type semiconductor</term> because the primary carriers of charge (electrons) are negative.</para>

Referencing norms: DonorImpurityGivesNType, doped_with_donor_impurity

en · official · sha256:3315c182468b27f0fb1209ada9388734b02deb1d58b89247946dcf678a17fb38

<definition id="fs-id1172098389313"> <term>doping</term> <meaning id="fs-id1172096062939">alteration of a semiconductor by the substitution of one type of atom with another</meaning> </definition>

en · official · sha256:b9f64a30978a6421a3572b733a2d21307cd0ecd187699fb91a645004b09a8f5a

<definition id="fs-id1172096188454"> <term>hole</term> <meaning id="fs-id1172098361688">unoccupied states in an energy band</meaning> </definition>

en · official · sha256:3885826627912f595a21e4c947bcb4626b84dcd18e72fcc46d5a524feafd74fc

<definition id="fs-id1172101010613"> <term>majority carrier</term> <meaning id="fs-id1172098643396">free electrons (or holes) contributed by impurity atoms</meaning> </definition>

Referencing norms: NTypeMajorityCarriersAreElectrons, PTypeMajorityCarriersAreNotElectrons

en · official · sha256:daae4a803ecb5cb7a43e45bc8aec4f652677a6076fa7cdbbe22b735bcf5762f0

<definition id="fs-id1172100595362"> <term>minority carrier</term> <meaning id="fs-id1172098592136">free electrons (or holes) produced by thermal excitations across the energy gap</meaning> </definition>

en · official · sha256:148b450887b849e0f7845dd4697cd765ed7e0f4a47a1864e6b09144ee594a8e5

<definition id="fs-id1172098524589"> <term><emphasis effect="italics">n</emphasis>-type semiconductor</term> <meaning id="fs-id1172098419284">doped semiconductor that conducts electrons</meaning> </definition>

en · official · sha256:9b836a0f8fa7ce20426ba4e1753dc1a40ee766561a7c5f61f5b7abafd59f0706

<definition id="fs-id1172096216106"> <term><emphasis effect="italics">p</emphasis>-type semiconductor</term> <meaning id="fs-id1172098392100">doped semiconductor that conducts holes</meaning> </definition>

Referencing norms: PTypeMajorityCarriersAreHoles