LOW-TEMPERATURE NEUTRON-IRRADIATION DAMAGE AND ITS RECOVERY IN HIGH-PURITY GERMANIUM

Abstract

Neutron-irradiation damage at 1.9 and 4.2 °K and its recovery to 300 °K were investigated in high-purity germanium by means of photoconductivity measurements. It was observed that the photoresistivity increased linearly with the irradiation time up to doses of 5 × 10¹² fission–neutrons/cm² for samples containing approximately 7 × 10¹³ impurity atoms/cm³, but that some saturation occurred for less pure samples (containing 10¹⁵ impurity atoms/cm³). Almost complete recovery of the irradiation-induced changes in photoresistivity of the higher-purity n- and p-type samples occurred in three stages, centered at 32, 95, and 180 °K. The results were independent of the method and degree of carrier excitation. The damage rates and recovery were explained in terms of the recombination of photocarriers through the simple vacancy and interstitial-type defects which were created by the irradiation and were subsequently removed by thermal migration.