The nature of thermoacceptors in electron-irradiated high-resistance silicon

Abstract

We have carried out an analysis of the possibility for the deep acceptor centers in silicon to participate in the formation of the thermoacceptor effect observed experimentally in a number of works, which consists in a change of conductivity from the n- to the p-type by annealing after irradiation of high-resistance silicon with electrons or neutrons. Based on the solution of the electroneutrality equation in a compensated monocrystalline silicon, we have estimated the concentration of the deep acceptor centers which are needed for obtaining p-type conductivity depending on the acceptor ionization energy and concentration of a shallow donor impurity. It is shown that deep acceptor centers (with ionization energy of up to 0.4 eV) can substantially contribute to the thermoacceptor effect in high-resistance n-type silicon prepared by floating zone melting. The concentrations of deep acceptors needed to overcompensate a sample with a low initial donor concentration (10¹²–10¹³ cm^–3) are on the order of 10¹²–10¹⁴ cm^–3 and seem to be quite achievable. Such centers can be divacancy–impurity (Fe, P) complexes with the ionization energy of up to 0.34 eV. In this case, the thermal activation of interstitial boron is also not excluded.