SPIN-DEPENDENT PHOTOCONDUCTIVITY IN CVD-GROWN AND MBE-GROWN SILICON-ON-SAPPHIRE

Spin-dependent photoconductivity is observed in (100) silicon films gr own on sapphire by CVD and MBE. The CVD films are either in their as-g rown state or have undergone single or double solid-phase epitaxial re growth. For all samples a resonant decrease in photoconductivity is ob served 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 fra ctional change in photoconductivity at resonance is measured as a func tion of the magnetic field strength, microwave or radiofrequency power , temperature, light intensity and sample voltage. The results are int erpreted in terms of a quantum mechanical treatment of the pair model of Kaplan, Solomon and Mott and values are extracted for the spin rela xation time, pair dissociation rate and singlet recombination rate. In some samples a resonant change in dark conductivity is also observed and interpreted.