Question

Carbon, silicon and germanium have four valence electrons each. These are characterised by valence and conduction bands separated by energy band gap respectively equal to $(E_g)_C, (E_g)_{Si}$ and $(E_g)_{Ge}$. Which of the following statements is true?

• A. $(E_g)_{Si} < (E_g)_{Ge} < (E_g)_C$
• B. $(E_g)_C < (E_g)_{Ge} > (E_g)_{Si}$
• C. $(E_g)_C > (E_g)_{Si} > (E_g)_{Ge}$
• D. $(E_g)_C = (E_g)_{Si} = (E_g)_{Ge}$

Answer 1

Answer: (C)

$(E_g)_C > (E_g)_{Si} > (E_g)_{Ge}$

Answer 2

For given three elements, he energy band gap of carbon is the maximum and that of germanium is the least. The energy band gap of these elements are related as:$(E_g)_C > (E_g)_{Si} > (E_g)_{Ge}$
Therefore, the correct statement is (c).