What is doping in semiconductors

Doping / doping

Doping or doping is understood to be the targeted change in the conductivity of semiconductors by incorporating foreign atoms into the pure semiconductor material. One also speaks of contaminating.

Donor / donor atom (n-layer)

The donor is the atom with which the semiconductor material for the n-layer is contaminated.
Donator comes from donare. This is Latin and means to give. Each donor atom gives the material an additional electron. This electron is free and can contribute to the creation of a current. Every electron that is added to the crystal by doping an atom increases the conductivity of the semiconductor.
Since every electron in the corresponding atomic nucleus is opposed to a proton, the semiconductor material remains electrically neutral due to the doping.
Donors or donor atoms are, for example:

  • Phosphorus (P) in the form of PH3, PCl3 or POCl3
  • Arsenic (As) in the form of AsH3 or as2O5
  • Antimony (Sb)

Acceptor / acceptor atom (p-layer)

The acceptor is the atom with which the semiconductor material for the p-layer is contaminated.
Acceptor comes from accipere. This is Latin and means to accept. The acceptor atoms are missing an electron. This leads to a hole in the semiconductor. There is an open crystal bond in the crystal. If an electron comes close to an open crystal bond due to the thermal movement, then it is drawn into this open bond. At that point the hole disappears. The bond is complete. At another point there is a hole or an open bond. An electron is constantly being drawn into a hole and a new one is created in another place. When there is no tension, the holes move in a disorderly manner.
Despite the resulting free charge carriers (holes), the charge on the semiconductor material remains electrically neutral due to the doping.
Acceptors are for example:

  • Aluminum (Al)
  • Gallium (Ga)
  • Indium (In)
  • Boron (B) in the form of B2H6, BCl3 or BN

n-doping

If phosphorus (P) is built into pure silicon, one free electron is available for each phosphorus atom (donor). Since the free electrons are negatively charged charge carriers, one speaks of an n-conductor.

If you connect a current source to the n-conductor, the positive pole withdraws the electrons from the n-conductor. An electron flow is created from minus to plus.

p-doping

If aluminum (Al) is built into pure silicon, one electron is missing for each aluminum atom (acceptor). Defect electrons are formed, which are also called holes. Since the holes are due to a lack of electronics or a positive charge, one speaks of a p-conductor.

If you connect a current source to the p-conductor, electrons flow from the minus pole into the p-conductor and recombine with the holes. The plus pole now withdraws the electrons from the p-conductor. A hole current flows from plus to minus.

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