In the energy band diagram of a material shown below, the open circles and filled circles denote holes and electrons respectively. The material is
Answer & explanation
Correct answer: option 4
For a p-typt semiconductor, the acceptor energy level, as shown in the diagram, is slightly above the top $E_v$ of the valence band. With very small supply of energy an electron from the valence band can jump to the level $E_A$ and ionise acceptor negatively.