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What are semiconductor types?

Semiconductors are materials with electrical conductivity between conductors and insulators. Their behavior can be modified by introducing dopant atoms, creating three distinct types:
  • Intrinsic semiconductors — Pure materials with balanced charge carriers
  • N-type semiconductors — Materials with excess electrons (negative charge carriers)
  • P-type semiconductors — Materials with excess holes (positive charge carriers)

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How SemiCode determines material type

The classification is based on the valence electron count of the host and dopant elements: 
export const determineMaterial = (el1, el2) => {
  const v1 = el1.valenceElectrons;
  const v2 = el2.valenceElectrons;

  if (v1 === 4 && v2 === 4) return "Intrínseco (Aislante)";
  if ((v1 === 4 && v2 === 5) || (v1 === 5 && v2 === 4)) return "Tipo N (Exceso de electrones)";
  if ((v1 === 4 && v2 === 3) || (v1 === 3 && v2 === 4)) return "Tipo P (Exceso de huecos)";
  return "Ninguno de los anteriores";
};
The function checks both orderings (host-dopant and dopant-host) to ensure correct classification regardless of input order.

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Intrinsic (pure) semiconductors

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Definition

An intrinsic semiconductor is a pure material with 4 valence electrons paired with another element that also has 4 valence electrons.

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Examples

  • Silicon + Silicon (14 + 14)
  • Germanium + Germanium (32 + 32)
  • Silicon + Germanium (14 + 32)

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Properties

  • Each atom forms 4 covalent bonds with neighbors
  • Complete tetrahedral crystal structure
  • Equal numbers of electrons and holes
  • Low conductivity at room temperature
  • Conductivity increases with temperature
Intrinsic semiconductors are labeled “Aislante” (Insulator) in the application because pure semiconductors have very low conductivity at room temperature.

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Crystal structure

In an intrinsic semiconductor: 
 Si — Si — Si
 |    |    |
 Si — Si — Si
 |    |    |
 Si — Si — Si
Each atom shares electrons equally with its neighbors, forming a perfect lattice with no excess carriers.

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N-type semiconductors

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Definition

An N-type semiconductor forms when a 4-valence-electron element (like Silicon) is doped with a 5-valence-electron element (like Phosphorus).

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Examples

  • Silicon + Phosphorus (14 + 15) → N-type
  • Silicon + Arsenic (14 + 33) → N-type
  • Germanium + Antimony (32 + 51) → N-type

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Properties

  • The dopant contributes one extra electron per atom
  • Excess electrons become free charge carriers
  • Increased electrical conductivity
  • Negative charge carriers (electrons) are majority carriers
  • Holes are minority carriers

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Crystal structure

 Si — Si — Si
 |    |    |
 Si — P — Si  ← Phosphorus has 5 valence electrons
 |   [e-]  |      One electron is free
 Si — Si — Si
The extra electron from Phosphorus doesn’t participate in bonding and becomes a mobile charge carrier.

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Visualization in SemiCode

In the lattice visualization:
  • The dopant atom is shown in orange
  • The free electron appears as a pulsing red circle (e⁻)
  • The Fermi level moves closer to the conduction band

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P-type semiconductors

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Definition

A P-type semiconductor forms when a 4-valence-electron element is doped with a 3-valence-electron element (like Boron or Aluminum).

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Examples

  • Silicon + Boron (14 + 5) → P-type
  • Silicon + Aluminum (14 + 13) → P-type
  • Germanium + Gallium (32 + 31) → P-type

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Properties

  • The dopant has one fewer electron than needed for bonding
  • Creates a “hole” (absence of electron) in the lattice
  • Holes act as positive charge carriers
  • Increased electrical conductivity
  • Holes are majority carriers
  • Electrons are minority carriers

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Crystal structure

 Si — Si — Si
 |    |    |
 Si — Al — Si  ← Aluminum has only 3 valence electrons
 |   [h+]  |      One bond is incomplete (hole)
 Si — Si — Si
The missing electron creates a hole that can move through the lattice as neighboring electrons fill the gap.

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Visualization in SemiCode

In the lattice visualization:
  • The dopant atom is shown in orange
  • The hole appears as a hollow dashed circle with h⁺ label
  • The Fermi level moves closer to the valence band

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Comparison table

PropertyIntrinsicN-typeP-type
Dopant valence453
Majority carriersEqual e⁻ and h⁺Electrons (e⁻)Holes (h⁺)
Fermi levelMidgapNear conduction bandNear valence band
ConductivityLowHighHigh
ExampleSi + SiSi + PSi + B
Color (lattice)Blue onlyBlue + Orange (with e⁻)Blue + Orange (with h⁺)

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Invalid combinations

Not all element pairs produce useful semiconductors. The function returns “Ninguno de los anteriores” (None of the above) for:
  • Both elements have 3 valence electrons (e.g., B + Al)
  • Both elements have 5 valence electrons (e.g., P + As)
  • Elements with 1, 2, 6, 7, or 8 valence electrons
  • Combinations outside the 3-4-5 pattern
Doping with elements outside group 13-15 (valence 3-5) typically doesn’t produce functional semiconductors and may damage the crystal structure.

Electronic configuration

Learn how valence electrons are determined from atomic structure

Doping

Understand the process of adding dopant atoms to semiconductors

Crystal lattice

Visualize how dopants and charge carriers appear in the crystal structure

Energy bands

See how Fermi levels differ between semiconductor types

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