The Nature of Thermal Acceptors in Electron Irradiated High Resistivity Silicon
This work is an analysis of the possible role of deep acceptor centers in silicon in the formation of the experimentally observed thermal acceptor effect consisting in the change from n to p conductivity type after annealing of electron or neutron irradiated high resistivity silicon. Based on the solution of the electrical negativity equation for compensated silicon we have estimated the dependence of the concentration of deep acceptor centers that is required for changing to p-type conductivity on acceptor energy level and shallow donor concentration. We show that deep acceptor centers can make a significant contribution to the thermal acceptor effect in high resistivity silicon (energy levels of up to 0.4 eV). The concentrations of deep acceptor centers required for changing the conductivity type are of the order of 10 12-10 14 cm -3. These concentrations seem to be achievable in samples containing low shallow donor concentrations (10 12-10 13 cm -3). Such centers can be divacancy-impurity complexes (Fe, P) with ionization energies of up to 0.34 eV. The thermal activation of interstitial boron is not excluded either.