The transient capacitance technique has been used to study the chromium-related levels in the silicon band gap. Chromium was diffused at temperature of 1100 and 1150°C for 0.5 and 3 hr. Five different levels at Ec-0.11 eV, Ec-0.21 eV, Ec-0.28 eV, Ec-0.36 eV and Ec-0.45 eV were obtained from the Arrheniu plots of the electron thermal-emission rates. The number of levels in the upper half of the band gap decreased from five to two with an increase of Cr-diffusion period. Two levels were located at Ec-0.20 eV (donor) and Ec-0.43 eV (acceptor). A donor level was also observed at Ev + 0.25 eV. The donor level was not affected by the diffusion condition. The majority carrier capture cross sections of the three dominant levels have been measured by the transient capacitance technique modified by the pulse transformer. The values were σn = 4.1 × 10-15 cm2 for the upper donor at Ec-0.20 eV, σn = 2.0 × 10-16 cm2 for the acceptor at Ec -0.43 eV and σp = 9.1 × 10-18 cm2 for the lower donor at Ev + 0.25 eV, and were independent of temperature. The three dominant levels are due to distinct chromium centers.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Materials Chemistry
- Electrical and Electronic Engineering