13.1.2 Exploring p-n junctions

• A p-type semiconductor is doped with trivalent impurities.
• What type of charge carriers are dominant in an n-type semiconductor?

  Free electrons
• What is the main charge carrier in an n-type semiconductor?

  Electrons
• What is the depletion region in a p-n junction depleted of?

  Free charge carriers
• The depletion region in a p-n junction is free of mobile charge carriers.

  True
• Match the property with the correct semiconductor type:

  Trivalent dopant ↔️ p-type

  Pentavalent dopant ↔️ n-type
• The depletion region in a p-n junction forms a built-in potential.
• When p-type and n-type semiconductors are brought together, the free electrons in the n-type region diffuse into the p-type region, and the electron holes in the p-type region diffuse into the n-type region. This process is called diffusion
• What is the built-in potential in a p-n junction?

  Electric potential across depletion region
• A p-type semiconductor has excess free electrons.

  False
• Steps in the formation of a p-n junction

  1️⃣ Diffusion of free electrons and holes

  2️⃣ Formation of the depletion region

  3️⃣ Creation of built-in potential
• The p-n junction is formed when a p-type semiconductor is brought into contact with an n-type
• The diffusion current in a p-n junction is caused by a concentration gradient
• Steps in the formation of the depletion region at a p-n junction

  1️⃣ Free electrons in the n-type region diffuse into the p-type region

  2️⃣ Electron holes in the p-type region diffuse into the n-type region

  3️⃣ Electrons and holes recombine, leaving behind immobile ions

  4️⃣ A built-in potential forms across the depletion region
• What is the role of the built-in potential in a p-n junction?

  Prevents further diffusion
• Which current is dominant under forward bias in a p-n junction?

  Diffusion current
• Under forward bias, the depletion region width decreases.


  True
• Under reverse bias, the built-in potential at a p-n junction is increased
• Under reverse bias, the overall current flow is dominated by the drift current.
• A p-type semiconductor has electron holes as its primary charge carriers.
• In the formation of a p-n junction, free electrons in the n-type region diffuse into the p-type region.
• The built-in potential acts as a barrier to further diffusion of charge carriers.

  True
• The depletion region is the area at the p-n junction where there are no free charge carriers
• Match the current type with its cause:

  Diffusion Current ↔️ Concentration gradient

  Drift Current ↔️ Electric field
• The built-in potential acts as a barrier to further diffusion of charge carriers.

  True
• Under forward bias, the drift current is minimal because it is not supported by the applied voltage.


  True
• Under forward bias, the dominant current is the diffusion current.


  True
• The I-V characteristic of a p-n junction shows a low resistance under forward bias and a high resistance under reverse bias.
• An n-type semiconductor is doped with pentavalent impurities.
• The main charge carriers in a p-type semiconductor are holes.
• During the formation of a p-n junction, electrons and holes recombine near the junction, neutralizing each other.
• The built-in potential at a p-n junction acts as a barrier to prevent further diffusion of charge carriers.

  True
• What are two common semiconductor devices that rely on the p-n junction?

  Diodes and transistors
• N-type semiconductors are doped with pentavalent impurities to produce excess free electrons.
• What process is responsible for creating the depletion region in a p-n junction?

  Diffusion
• What is the depletion region in a p-n junction?

  Area with no free carriers
• The built-in potential across the depletion region acts as a barrier to further diffusion of charge carriers.


  True
• Match the type of semiconductor with its primary dopant and charge carrier:

  p-type semiconductor ↔️ Boron and Holes

  n-type semiconductor ↔️ Phosphorus and Electrons
• The diffusion process in a p-n junction creates a depletion region and a built-in potential
• In a drift current, charge carriers move opposite to the direction of the electric field.


  True