Influence of hydrogen and temperature on positron trapping in proton-irradiated silicon

Positron lifetime measurements are used to investigate positron trapping in silicon irradiated with protons at a high dose of 3.2 x 1017 cm-2 and a lower dose of 3.6 x 1016 cm-2, respectively. The irradiation-induced vacancy defects are mainly divacancies. During the irradiations, the divacancies in high dose samples have almost trapped hydrogen, while a part of the divacancies in low dose samples have not trapped hydrogen yet. In the measurements of the two warm-up of high dosed samples and the first warm-up of low dose samples, the further trapping of hydrogen into divacancies is observed. With the increasing of temperature the charge state of the divacancies decorated by hydrogen takes a transition from negative to neutral around 145 K. With the increasing of the amount of the trapped hydrogen per divacancy, the lifetimes of the negatively charged divacancy and the neutral one are both shortened, while both their trapping cross sections are increased. The trapping of hydrogens into the negatively charged divacancies has no influence on the temperature dependence of its trapping cross sections