Field‐Enhanced Ionization

At field strengths which can lie markedly below the critical values for impact ionization and Zener extraction, field induced changes in the capture cross section, barrier height, and frequency factor of Coulomb‐attractive centers due to a deformation of the potential around the center and induced by the external field can cause a marked redistribution of carriers over these centers (field‐enhanced ionization). These changes in the kinetic parameters of the centers are estimated, using a classical model, and are given as a function of the external field. For a typical semiconductor at T = 200 °K, a possible decrease of trap‐occupation up to a factor of two, already, at fields of the order of 10 2 V/cm is calculated.