Question

Which of the following semiconductors is electrically negative?

• A. Intrinsic semiconductor
• B. Silicon doped with pentavalent impurities
• C. Silicon doped with trivalent impurities
• D. None of the alternatives (A), (B) and (C) is correct

Hint:

Remember: \[ \text{Pentavalent doping} \Rightarrow n\text{-type} \] \[ \text{Trivalent doping} \Rightarrow p\text{-type} \] \(n\)-type semiconductors are electrically negative because electrons are the majority carriers.

Answer 1

The Correct Option is B

Concept: A semiconductor is called electrically negative when electrons are the majority charge carriers. Such semiconductors are called \(n\)-type semiconductors.

Step 1: Recall the effect of doping. \[ \begin{aligned} \text{Pentavalent} &\rightarrow n\text{-type} \rightarrow \text{Electrons} \\ \text{Trivalent} &\rightarrow p\text{-type} \rightarrow \text{Holes} \end{aligned} \]

Step 2: Identify the electrically negative semiconductor. Pentavalent impurities contribute extra electrons. Hence, \[ \text{electrons}\gt \text{holes}. \] Therefore the semiconductor behaves as an electrically negative semiconductor. \[\begin{aligned} \boxed{\text{Silicon doped with pentavalent impurities}} \end{aligned}\] Hence, option \(\mathbf{(B)}\) is correct.