The energy band diagram is used to indicate that the atom and the silicon atom are replaced by a covalent bond, and the binding energy at the top of the valence band is slightly higher. At the location, a narrow acceptor level is formed.

As the temperature rises, the valence band electrons are excited at the acceptor level and holes appear in the valence band. Conversely, it can also be explained that holes are released from the acceptor level and supplied to the valence band. We all know that the effective mass of the valence band electron is larger than that of the conduction band electron, so the binding energy of the acceptor level is greater than the binding energy of the donor. The brick (B) is 45 meV, the aluminum (A1) is 69 meV, and the calcium (Ca) is 72 meV, indium (ln) is 160 meV. Although they are shallow, sodium (Na) is 350 meV, 钡 (Ba) is 430 meV, etc., at a higher energy level, forming a hole-trapping center.