Effect of electron trap states on spin-dependent transport characteristics in CoFe/MgO/n+-Si junctions investigated by Hanle effect measurements and inelastic electron tunneling spectroscopy

Abstract

Spin-dependent transport properties in CoFe/MgO/n+-Si junctions were investigated by Hanle effect measurements and inelastic electron tunneling (IET) spectroscopy. The CoFe/MgO/n+-Si junctions examined in this study exhibited two different Hanle curves. In the low bias region, broad Hanle signals were mainly observed; in the high bias region, narrow Hanle signals were mainly observed. The d2I/dV2-V curves (which correspond to IET spectra) contain several peaks originating from phonon modes and other peaks originating from electron trap states. At the bias voltage where electron trap states are observed, Δd2I/dV2 depends on the magnetic field and the full width at half-maximum of the Δd2I/dV2–H curves corresponds to that of the broad Hanle signals. These results indicate that electron trap states are located in the low energy region and cause a decrease in spin lifetime.