Question

Which of the following energy band diagram shows the n-type semiconductor :-

• A.

  \begin{array}{|c|} \hline Conduction \\ Band \\ \hline \end{array}
  

  $E_g$=1eV

  \begin{array}{|c|} \hline Valence \\ Band \\ \hline \end{array}
  

• B.

  \begin{array}{|c|} \hline Conduction \\ Band \\ \hline \end{array}
  

  Impurity level 1eV

  \begin{array}{|c|} \hline Valence \\ Band \\ \hline \end{array}
  

• C.

  \begin{array}{|c|} \hline Valence \\ Band \\ \hline \end{array}
  

  Impurity level 1 eV

  \begin{array}{|c|} \hline Conduction \\ Band \\ \hline \end{array}
  

• D.

  \begin{array}{|c|} \hline Valence \\ Band \\ \hline \end{array}
  

  \begin{array}{|c|} \hline Conduction \\ Band \\ \hline \end{array}
  

  1 eV Impurity level

Answer 1

Answer: (D)

Option (4)

Answer 2

To determine which energy band diagram represents an n-type semiconductor, we need to understand the characteristics of an n-type semiconductor's energy band structure.

Key Concepts for n-type Semiconductors:

1. Doping: N-type semiconductors are formed by adding pentavalent impurities (donor atoms) to an intrinsic semiconductor.
2. Donor Energy Level: These donor atoms introduce a new discrete energy level, called the donor energy level ($E_D$), within the forbidden band gap.
3. Position of Donor Level: The donor energy level is located just below the conduction band ($E_C$). The energy difference between the donor level and the conduction band is very small (typically 0.01 eV to 0.05 eV for common semiconductors like Ge and Si).
4. Electron Contribution: At room temperature, electrons from these donor levels easily gain enough thermal energy to jump into the conduction band, significantly increasing the number of free electrons.
5. Majority Carriers: Electrons are the majority charge carriers in n-type semiconductors.

Based on the standard energy band diagram conventions for semiconductors, option (4) correctly depicts the energy band structure of an n-type semiconductor.