Spectroscopic analysis demonstrates dual charge states of cobalt centers in doped silicon, modifying kinetics of negative photoconductivity models.
Key Points
To investigate extrinsic optical absorption and transient photoconductivity resulting from deep cobalt impurity levels in silicon.
Measured extrinsic optical absorption spectra across long wavelengths in cobalt-doped silicon.
Evaluated transient response times of positive and negative photoconductivity to determine carrier kinetics and impurity charge states.
Demonstrated that the acceptor level at 0.52 eV below the conduction band and donor level at 0.38 eV above the valence band belong to the same cobalt center in different charge states.
Showed that excited states of neutral and positively charged cobalt centers account for optical absorption profiles and modify two-level kinetic models of negative photoconductivity.