High field current induced-positive charge transients in SiO₂

The formation of bulk positive charge in SiO₂ induced by charge injection and high field conditions is studied in this work, utilizing new experimental methods. Using a dc hot electron injection technique it is shown that the presence of electrons in the SiO₂ conduction band is a necessary condition for the positive charge formation. This result rules out field (only) induced mechanisms as possible explanations of high field positive charge generation in SiO₂. The positive charge formation and annihilation are found to be governed by the same rate equation, and, therefore, exhibit similar behavior as a function of time. This behavior is consistent with an impact ionization-recombination model, with a recombination cross section σ=2×10^-16 cm² and ionization rate α which is in agreement with previous published values. However, other collision activated mechanisms cannot be ruled out.