Injection-limited trap modulated hopping conduction in carbonyl doped polyethylene

A recently developed theory of steady-state conduction of space charge limited (SCL) currents in polyethylene doped with carbonyl hopping sites, and including detrapping, is modified to apply to the injection limited case, i.e., to a nonzero field F0 at the injecting electrode. Good agreement with experiment was previously obtained for SCL carriers (F0=0) for applied fields up to 0.33 MV/cm. Here, we assume that for higher fields, F0 is proportional to the difference between the applied field and 0.33 MV/cm. Excellent agreement between theory and experimental current-applied field characteristics is then obtained for fields up to 0.5 MV/cm. The field distributions in doped and ‘‘pure’’ polyethylene samples are calculated, and are found to be independent of temperature in the range 49–82 °C for constant field.