N-type and P-type semiconductors are formed by doping pure semiconductor materials, such as silicon or germanium, with specific impurities that alter their electrical properties.
Formation of N-type Semiconductor
- An N-type semiconductor is created by doping the pure semiconductor with pentavalent impurities-elements from group V of the periodic table like phosphorus, arsenic, antimony, or bismuth. These elements have five valence electrons.
- When introduced into the semiconductor lattice, four of the impurity's electrons form covalent bonds with the surrounding silicon atoms, while the fifth electron remains free to move.
- This free electron increases the number of negative charge carriers (electrons) in the material, enhancing its conductivity.
- Because the majority carriers are negatively charged electrons, the material is called an N-type (negative-type) semiconductor
Formation of P-type Semiconductor
- A P-type semiconductor is formed by doping the pure semiconductor with trivalent impurities-elements from group III such as boron, gallium, aluminum, or indium, which have three valence electrons.
- These impurities create "holes" or deficiencies of electrons in the semiconductor's valence band because they have one less electron to form bonds.
- These holes act as positive charge carriers, enabling electrical conduction.
- Since the majority carriers are positively charged holes, the material is called a P-type (positive-type) semiconductor
Summary of the Doping Process
- Doping involves heating the pure semiconductor in the presence of the chosen impurity so that the impurity atoms diffuse into the crystal lattice.
- The resulting doped semiconductor has significantly enhanced electrical conductivity due to the increased number of charge carriers-electrons in N-type and holes in P-type semiconductors
This controlled introduction of impurities is essential for manufacturing electronic components like diodes, transistors, and integrated circuits, where N-type and P-type materials are combined to form p-n junctions critical for device operation.
