Question

Why are only silicon and germanium taken as semiconductor semiconductors while carbon,tin and lead also have four electrons in their outermost shell

Answer 1

Dear Student, A certain band gap of less than 2.5eV is required for a semiconductor. In Carbon, elctrons are nearer to nucleus. So, they are tightly bound due to which there are very less number of free electrons in it. Even for generating more free electrons, high ionisation energy is required. Thus, band-gap is higher in Carbon. In Tin and Lead, electrons are very loosely bound due to which there are many free electrons in it even at room temperature. So, conduction and valence bands overlap in them making them conducting metals. So, Silicon and germanium are widely used as semiconductors as their band-gap lies in the required range. Regards