The Effect of Dislocations on the Activation Energy of Radiation Defect Thermal Ionization

Abstract

The effect of dislocations introduced at plastic deformation (ND= 1 × 105 to 2 × 107 cm−2) on the activation energy δE of radiation defect thermal ionization in Si is studied. The temperature (80 to 400 K) dependences of the Hall coefficient at various steps of 60Co γ‐ray irradiation are mea‐sured. A variation in δE is found to take place for point defects accumulating near dislocations (A‐centres, divacancies, interstitial carbon‐substitutional carbon complex, carbon‐oxygen‐di‐vacancy complex). An increase of δE with ND increasing is characteristic of A‐centres, for example, for low integral γ‐ray fluxes (Φ ⪅ 5 × 1016 cm−2). This is due to the increase of thermal ionization energy ΔE as a result of shifting of allowed band edges and defect levels, because of the crystal lat‐tice deformation near dislocations. In dislocated Si (ND ⪆ 1 × 106 cm−2) on increasing Ø one ob‐serves at first a decrease of δE, and then its increase. It is connected with the formation of radia‐tion defect agglomerations near dislocations which have a localize dspatial charge and produce a potential barrier Ψ, whereby δE = ΔE =Ψ. The dose dependences of δE are explained taking into account the variation in Ψ with increasing Ø and the possibility of defect rearrangements in more complicated complexes near dislocations.