Carbon, silicon and germanium atoms have four valence electrons each. Their valence and conduction bands are…

Carbon, silicon and germanium atoms have four valence electrons each. Their valence and conduction bands are separated energy band gaps represented $\left(E_g\right)_C,\left(E_g\right)_{S i}$, and $\left(E_g\right)_{G e}$ respectively. Which one of the following relationship is true in their case?
  1. $\left.\left(\mathrm{E}_g\right)_{\mathrm{C}} > \mathrm{E}_g\right)_{\mathrm{Si}}$
  2. $\left.\left(\mathrm{E}_g\right)_{\mathrm{C}} < \mathrm{E}_g\right)_{\mathrm{Si}}$
  3. $\left.\left(\mathrm{E}_g\right)_{\mathrm{C}}=\mathrm{E}_g\right)_{\mathrm{Si}}$
  4. $\left(\mathrm{E}_g\right)_{\mathrm{C}} > \left(\mathrm{E}_g\right)_{\mathrm{Ge}}$

Solution

Band gap of carbon is $5.5 \mathrm{eV}$ while that of silicon is $1.1 \mathrm{eV}$ $\left(E_g\right)_C > \left(E_B\right)_S$

Asked in: NEET 2005

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