 Regarding the typology of traps, the Poole-Frenkel effect is described to occur for positively charged trap sites, i.e.for traps that are positive when empty and neutral when filled, in order for the electron to experience a Coulombic potential barrier due to the interaction with the positively charged trap.Donors or acceptors sites and electrons in the valence band will also exhibit the Poole-Frenkel effect as well.