Which of the following can be used as an n-type dopant for silicon?

Select the correct option(s).

For non-degenerately doped n-type silicon, which one of the following plots represents the temperature ($T$) dependence of free electron concentration ($n$)?

The free electron concentration profile $n(x)$ in a doped semiconductor at equilibrium is shown in the figure, where the points A, B, and C mark three different positions. Which of the following statements is/are true?

In a semiconductor, if the Fermi energy level lies in the conduction band, then the semiconductor is known as