Titanium in silicon as a deep level impurity

Abstract

Titanium inserted in silicon by diffusion or during Czochralski ingot growth is electrically active to a concentration level of about 4 × 10 14 cm −3. Hall measurements after diffusion show conversion of lightly doped p type Si to n type due to a Ti donor level at E C - 0.22 eV. In DLTS measurements of n + p structures this level shows as an electron (minority carrier) trap at E C - 0.26 eV with an electron capture cross section of about 3 × 10 −15 cm 2 at 300°K. The DLTS curves also reveal a hole trap in the p type material. The e p (300/ T) 2 activation plot gives the level as E V + 0.29 eV. The hole capture cross section is about 1.7 × 10 −17 cm 2 at 300°K and decreases with decreasing temperature and the corrected trap level becomes E V = 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 × 10 13 cm −3 in p type ( N A = 3.35 × 10 15 cm −3) Si results in a minority carrier (electron) lifetime of 50 nsec at 300°K.