Question

Carbon, silicon and germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy band gaps represented by ${\left(E_g\right)}_c,{\left(E_g\right)}_{Si}$ and ${\left(E_q\right)}_{Ge}$ respectively. Which one of the following relationships is true in their case?

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

Answer 1

Answer: (A)

Carbon, silicon and germanium are semiconductors.
${\left(E_g\right)}_C=5.2eV$
${\left(E_g\right)}_{Si}=1.21eV$
${\left(E_g\right)}_{Ge}=0.75eV$
Thus, ${\left(E_g\right)}_C>{\left(E_g\right)}_{Si}$ and ${\left(E_g\right)}_C>{\left(E_g\right)}_{Ge}$
NOTE : Elements carbon, silicon and germanium are found in IVA group of periodic table.