Carrier Lifetime Studies in Electron-(10–55 MeV) and Proton-(25–110 MeV) Irradiated Germanium

Abstract

Samples of single-crystal germanium were irradiated at room temperature with electrons of energies from 12 to 55 MeV and with protons of energies from 25 to 109 MeV. Measurements of the minority carrier lifetime as a function of flux and initial carrier concentration suggest that: (1) More than one recombination level, active at room temperature, is introduced in the forbidden gap by the defects created during electron and proton bombardment, with the multilevel effect being greater for the proton-irradiated specimens. (2) The carrier lifetime change with increasing proton energy does not decrease as sharply as predicted by Rutherford scattering and the Kinchin-Pease model. This indicates that nuclear elastic and inelastic processes must be included in computing the number of primary knockons created by protons of energies above at least 50 MeV. (3) The energy dependence of carrier lifetime change in the case of electron bombardment is complicated by a non-constant contribution of multiple levels to the recombination process in the electron energy range studied. At 12 MeV the behavior is adequately represented by single-level theory and a value of 15.4 displacements/cm is obtained.