TITANIUM IN SILICON AS A DEEP LEVEL IMPURITY

Titanium inserted in silicon by diffusion or during Czochralski ingot growth is electrically active to a concentration level of about 4 × 1014 cm-3. Hall measurements after diffusion show conversion of lightly doped p type Si to n type due to a Ti donor level at EC - 0.22 eV. In DLTS measurements of n+p structures this level shows as an electron (minority carrier) trap at EC - 0.26 eV with an electron capture cross section of about 3 × 10-15 cm2 at 300°K. The DLTS curves also reveal a hole trap in the p type material. The ep (300/T)2 activation plot gives the level as EV + 0.29 eV. The hole capture cross section is about 1.7 × 10-17 cm2 at 300°K and decreases with decreasing temperature and the corrected trap level becomes EV = 0.26 eV. Ti in lightly doped (360 ohm-cm) n type material does not result in conversion to p type so this level is inferred also to be a donor. A Ti electrically active concentration of about 1.35 × 1013 cm-3 in p type (NA = 3.35 × 1015 cm-3) Si results in a minority carrier (electron) lifetime of 50 nsec at 300°K. © 1999.