The energy gap of silicon is given as approximately:

1. The three group-four elements have very different band gaps. 2. Diamond is the largest and germanium the smallest. 3. For C, Si and Ge the energy gaps are 5.4 eV, 1.1 eV and 0.7 eV respectively. 4. So silicon is about 1.1 eV. _Source: syllabus Physics Part II, Ch 14 'Semiconductor Electronics'_