Spin-dependent photoconductivity in CVD- and MBE-grown silicon-on-sapphire

Spin-dependent photoconductivity is observed in (100) silicon films grown on sapphire by CVD and MBE. The CVD films are either in their as-grown state or have undergone single or double solid-phase epitaxial regrowth. For all samples a resonant decrease in photoconductivity is observed at a field of about 0.34 T for a microwave frequency of about 9.6 GHz and at about 3.3 mT when the frequency is about 92 MHz. The fractional change in photoconductivity at resonance is measured as a function of the magnetic field strength, microwave or radiofrequency power, temperature, light intensity and sample voltage. The results are interpreted in terms of a quantum mechanical treatment of the pair model of Kaplan, Solomon and Mott and values are extracted for the spin relaxation time, pair dissociation rate and singlet recombination rate. In some samples a resonant change in dark conductivity is also observed and interpreted