Interaction of Li and O with Radiation-Produced Defects in Si

The interaction of Li atoms with O impurities and with defects produced in Si by 1.5 MeV and 47 MeV electrons was studied using infrared spectroscopy. Li was diffused in low oxygen-containing uncompensated Si with initial resistivity in the range 15–28 500 Ω·cm and in high oxygen-containing Si with initial resistivity of 15–200 Ω·cm. The Li concentration in the samples varied from about 1016 to ≲1019 Li atoms/cm3. New radiation-induced bands at 1.4 and 1.7 μ are observed. Divacancy production as measured by the 1.8 and 3.3 μ defect bands is markedly decreased in samples of high Li content with concomitant growth of the Li-associated 1.4 and 1.7 μ bands. Annealing of the 1.4 and 1.7 μ bands strongly depends upon the Li concentration. Recovery occurs at a temperature of 150°C for the 1.4 μ band, and at 350°C for the 1.7 μ band, for samples containing ∼6×1017 Li/cm3. In samples containing ∼2×1016Li/cm3, the bands at 1.4 and 1.7 μ disappear after annealing at 330° and 470°C, respectively. Sharp Li- and O-associated defect bands in the 700–1000 cm−1 range are produced only in high O-containing samples, and the presence of Li has a pronounced effect on the production and recovery of the A-center defect (830 cm−1 band). In samples of high Li content, the predominant absorption is due to free carriers and is found to be in agreement with predictions of theory. A search for defect absorption bands attributable to vibrational modes of the isolated interstitial Li+ ions yielded negative results.