Transient Ionization Effects in Silicon Induced by 48 MeV Electron Pulses

Transient radiation effects induced in silicon irradiated in the temperature range 90 to 300°K by 0.007 to 4.5 microsecond pulses of 48 MeV electrons were studied using the transient response of resistivity and Hall effect voltages as the measuring probes. Results are given for one ohm-cm phosphorus-doped n-type silicon and 10 to 100 ohm-cm n-type and p-type samples. In the case of one ohmcm silicon the results clearly show the actual buildup of excess electrons produced by ionization during the time the electron pulse is irradiating the sample. Moreover, the shape of the pulse during buildup is independent of temperature as long as the electron beam pulse is kept constant. Dependence of the number of injected excess carriers on the ionization intensity (total integrated electron flux in the pulse) was found to be linear up to excess carrier concentrations of ~ 1017 cm-3. The lifetime is found to increase linearly with injection implying that the recombination may be dominated by one defect energy level. In p-type silicon the transient Hall and conductivity voltages decay in ~ 20-50 jsec. Relatively long saturation times (~ 10 to 100 microseconds) are observed in the transient Hall and conductivity voltage following an electron burst. The saturation time decreases with dose accumulation in p-type and also decreases as the irradiation temperature of the sample (both n- and p-type) is decreased. Very similar effects also are observed in n-type silicon samples.