സോളിഡ് സ്റ്റേറ്റ് ഫിസിക്സിൽ ബാന്റ് ഗ്യാപ് (band gap, energy gap, അല്ലെങ്കിൽ bandgap) എന്നെല്ലാം അറിയപ്പെടുന്നത് ഒരു ഖരത്തിൽ ഇലക്ടോണുകൾക്ക് സ്ഥിതി ചെയ്യാൻ സാധ്യമല്ലാത്ത ഒരു ഊർജ്ജ മേഖലയെയാണ്.
Showing how electronic band structure comes about by the hypothetical example of a large number of carbon atoms being brought together to form a diamond crystal. The graph (right) shows the energy levels as a function of the spacing between atoms. When the atoms are far apart (right side of graph) each atom has valence atomic orbitals p and s which have the same energy. However when the atoms come closer together their orbitals begin to overlap. Due to the Pauli Exclusion Principle each atomic orbital splits into N molecular orbitals each with a different energy, where N is the number of atoms in the crystal. Since N is such a large number, adjacent orbitals are extremely close together in energy so the orbitals can be considered a continuous energy band. a is the atomic spacing in an actual crystal of diamond. At that spacing the orbitals form two bands, called the valence and conduction bands, with a 5.5eV band gap between them. Very few electrons have the energy to surmount this wide energy gap and become conduction electrons, so diamond is an insulator.Semiconductor band structure.
Vella, E.; Messina, F.; Cannas, M.; Boscaino, R. (2011). "Unraveling exciton dynamics in amorphous silicon dioxide: Interpretation of the optical features from 8 to 11 eV". Physical Review B. 83 (17): 174201. Bibcode:2011PhRvB..83q4201V. doi:10.1103/PhysRevB.83.174201.
