Photo-EPR Investigations of Thermal Donors in Silicon

Two thermal donor related EPR centers Si-NL8 and Si-NL10 were studied by the photo-EPR technique. The spectral dependence of the intensity of the EPR signals was determined for the region from 0.6 to 1.4 eV in several samples with different Fermi level position. The quenching of the Si-NL8 signal with the coinciding enhancement of the Si-NL10 signal has been observed with possible indication of some metastable behavior of the NL8 center. For the heavily aluminum doped material strong generation of photocurrent upon band gap illumination has been observed. The results of the study provide further evidence for mutal correlation of both thermal donor related EPR centers since the observed spectral dependences could be understood by relating both NL8 and NL10 spectra to different paramagnetic states of basically the same center