A pure semiconductors

Options

A. extrinsic semiconductor
B. intrinsic semiconductor
C. n type semiconductor
D. p type semiconductor

Answer

**Step-by-Step Solution:**

1. **Definition of Pure Semiconductors:**
- Pure semiconductors are materials that have no significant impurities. They are characterized by their electrical properties, which are determined solely by the semiconductor's own atomic structure.

2. **Intrinsic Semiconductors:**
- Pure semiconductors are referred to as intrinsic semiconductors. In intrinsic semiconductors, the charge carriers (electrons and holes) are generated thermally. This means that at room temperature, some electrons gain enough energy to jump from the valence band to the conduction band, creating holes in the valence band.

3. **Carrier Concentration:**
- In intrinsic semiconductors, the concentration of charge carriers (holes and electrons) is very low because it relies on thermal excitation. The number of electrons (n) is equal to the number of holes (p) in an intrinsic semiconductor, which can be represented as n = p.

4. **Current in Intrinsic Semiconductors:**
- The total current (I) in an intrinsic semiconductor can be expressed as the sum of the hole current (I_h) and the electron current (I_e). Mathematically, this can be written as:
\[ I = I_h + I_e \]
- However, since the number of thermally generated carriers is small, the current is also small and may not be sufficient for practical applications.

5. **Doping to Enhance Conductivity:**
- To improve the conductivity of intrinsic semiconductors, they are often doped with impurities. Doping introduces additional charge carriers into the semiconductor.
- If a trivalent impurity (like Boron) is added, it creates holes, resulting in a p-type semiconductor. If a pentavalent impurity (like Phosphorus) is added, it donates extra electrons, resulting in an n-type semiconductor.

6. **Conclusion:**
- Therefore, the correct answer to the question "A pure semiconductor" is that it is known as an intrinsic semiconductor.

**Final Answer:**
- Pure semiconductors are known as intrinsic semiconductors.

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