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 (Eg)C, (Eg)Si and (Eg)Ge. Which of the following statements is true?

For an insulator, the band gap energy is always higher, (Eg≈ 6ev). And in case of silicon and germanium, silicon has higher energy gap than germanium. (This is experimental data.)

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