Poole–Frenkel emission by transient current measurements in semi‐insulating polycrystalline silicon containing 35 at. % O has been investigated. In the presence of intense electric fields the conductivity of the material is strongly enhanced by the emission of free carriers. By applying square wave voltage signals, the field strength is modulated, thus producing current transients. By the analysis of these transients we have measured the emissivity of the traps responsible for the Poole–Frenkel effect as a function of temperature. The emissivity shows an activated behavior and the corresponding binding energy of the trap results equal to ≊0.64 eV. ©1995 American Institute of Physics.