Revised role for the Poole–Frenkel effect in deep-level characterization

The Poole–Frenkel effect is commonly used to decide between donorlike and acceptorlike electronic character for deep-level defects in semiconductors. However, there exists at least one defect, the EL2 center in GaAs, which is experimentally established to be a deep donor and yet does not exhibit the classical Poole–Frenkel effect for thermal emission of electrons. In this communication it is proposed that the existence of another well-documented deep-level phenomenon can suppress the Poole–Frenkel effect. Namely, a thermally activated capture cross section, which identifies an energy barrier to carrier capture and is commonly ascribed to a multiphonon emission process, introduces additional mechanisms which can alter the predominance of the Coulombic potential of the emitted carrier so as to suppress the electric-field-induced barrier lowering. A simple one-dimensional model is analyzed to qualitatively illustrate the combined phenomena.