Question

Write two points of difference between intrinsic and extrinsic semiconductors.

Hint:

When a physics question simply asks for "two points of difference," always cleanly structure your answer in a clear two-column table or use distinct bullet points highlighting directly contrasting traits (e.g., Pure vs Impure, $n_e=n_h$ vs $n_e \neq n_h$) to guarantee maximum marks.

Answer 1

Concept:
• Semiconductors uniquely operate fundamentally between conductors and insulators, playing the starring role in all modern electronics.

• Intrinsic semiconductors represent the absolute purest, unadulterated form of the crystalline material (like pure Silicon or Germanium) found in nature, containing virtually zero chemical impurities.

• Extrinsic semiconductors, on the other hand, are strictly man-made versions that have been intentionally and aggressively "doped" with minute, highly controlled quantities of specific chemical impurities (like Phosphorus or Boron) to drastically and purposely alter their baseline electrical properties.

Step 1: Difference 1: Inherent Purity and Structural Composition
An intrinsic semiconductor is a perfectly pure semiconductor crystal totally free from any deliberately introduced foreign atoms or chemical defects.
An extrinsic semiconductor is a deliberately impure semiconductor. It is carefully manufactured by heavily doping a pure intrinsic semiconductor matrix with specifically chosen trivalent or pentavalent impurity atoms.

Step 2: Difference 2: Density of Charge Carriers
In any intrinsic semiconductor, because every single broken covalent bond inherently generates exactly one free electron and one corresponding hole simultaneously, the thermal number density of free electrons ($n_e$) is always absolutely equal to the thermal number density of holes ($n_h$). Mathematically, $n_e = n_h = n_i$.
In stark contrast, an extrinsic semiconductor exhibits a massive, intentional disparity. Depending entirely on the specific type of doping applied, one specific type of charge carrier vastly outnumbers the other. In n-type materials, electrons brutally dominate ($n_e \gg n_h$), whereas in p-type materials, holes aggressively dominate ($n_h \gg n_e$).

Step 3: Additional points for completeness
For added completeness, one could also validly mention Electrical Conductivity.
The intrinsic semiconductor possesses an exceptionally low baseline electrical conductivity at standard room temperature, heavily limiting its practical use in devices.
The extrinsic semiconductor boasts a tremendously high, artificially boosted electrical conductivity directly engineered by the sheer abundance of the added impurity dopants, making them essential for creating diodes and transistors.