Assertion (A) : The energy gap between the valence band and conduction band is greater in Silicon than in Germanium.

Reason (R) : Thermal Energy produces fewer minority carriers in Silicon than in Germanium.

Both A and R are true, but R is the NOT correct explanation of A 

• The energy gap between valence band and conduction band in germanium is 0.76 eV and the energy gap between valence band and conduction band in silicon is 1.1eV.
• It is true that thermal energy produces fewer minority carriers in silicon than in germanium.