STUDY OF AN ANDERSON NEGATIVE - U SYSTEM BY MEANS OF HALL-MOBILITY MEASUREMENTS IN SILICON

Boron-doped silicon samples have been irradiated by 5.4 GeV Xe ions. I n situ Hall effect measurements have been performed during irradiation to determine the hole concentration p/r(H) and the Hall mobility mu(H ). The Hall mobility presents a minimum when plotted as a function of the fluence. Simulations point to the fact that this minimum is consis tent with the negative-U properties of the silicon vacancy. More, by c omparing experimental and calculated p/r(H) and mu(H) curves, introduc tion rates are estimated as follows : eta(v) congruent-to 6 10(4) cm-1 for vacancies, eta(v2) congruent-to 2 10(3) cm-1 for divacancies and eta(Bi) congruent-to 5 10(3) cm-1 for boron interstitials.