The effect of dislocations introduced at plastic deformation (ND = 1 × 105 to 2 × 107 cm−2) on the radiation defect production and annealing processes in n‐ and p‐type Si single crystals (g = 20 to 1500 ω cm) irradiated (Tirr ≦ 320 K) by γ‐rays of 60Co or 640 MeV protons is studied. The temperature dependences of the Hall factor and the electrical conductivity are measured. It is found that the introduction efficiency and temperature stability of some defects are changed due to the higher dislocation density available in crystals. The results obtained are interpreted taking into account the fact that the elastic stress fields available around dislocations, which cause the vacancies and interstitial atoms to migrate towards dislocations, play the determining role for the radiation defect formation. Thereby two competitive processes proceed near dislocations: disappearance of the primary radiation defects and their participation in complex production. As a result, a decrease in the introduction rates of A‐, E‐centers, interstitial carbon, and the formation of a dislocation‐impurity‐defect atmosphere which comprises A‐centers, divacancies, oxygen‐car‐bon‐divacancy complexes, and defect cluster regions obtained during the proton irradiation, is found.
Recombination processes of nonequilibrium charge carriers at dislocations introduced at plastic deformation (Tdef = 750 °C) and radiation defects being generated by 60Co γ‐rays (Tirr ≦ 50 °C) are studied. p‐type Si single crystals (ϱ = 20 to 1500 Ω cm) are used grown by the float‐zone as well as by the Czochralski techniques. The lifetime (τ) of minority charge carriers is measured (Tmeas = 300 K) by the method of conductivity modulation at a point contact at different stages of plastic deformation and irradiation. The established regularities of the τ variation with increasing dislocation density (ND) for different charge‐carrier injection levels (Δp/p0) in plastically deformed and irradiated Si are explained on the basis of the model developed taking into account the presence of space charge regions near dislocations which produce potential barriers and wells for holes and electrons. This stipulates a spatial separation of nonequilibrium charge carriers and results in a decrease of their recombination rate at radiation defects distributed in the crystal matrix and accumulated near dislocations. The potential barrier height depends on ND and Δp/p0 and varies during irradiation due to the interaction of primary radiation defects with dislocations and changes in the dislocation structure.
The accumulation processes of the compensating and recombination centres during G°Co yray irradiation of n-type Si (p=50-250 Rcm, s=50-100 ps) with a high dislocation density ( N D = 1.104-1' lo7 cm-2) introduced by plastic deformation are studied. The results are obtained from measurements of the minority charge-carrier lifetime by the method of conductivity modulation at a point contact and the Hall coefficient temperature dependences. Radiation defect introduction efficiency is found to depend significantly on the content of the dislocation impurity atomosphere whose change is achieved by varying the deformation conditions (fast and slow cooling) and subsequent radiation-heat treatments (y-ray irradiation and annealing). The experimental results are interpreted taking into account the conception of compensation of elastic stress fields by impurity atoms and participation of impurities in complexing with primary radiation defects near dislocations.
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