High-resolution electrical detection of free induction decay and Hahn echoes in phosphorus-doped silicon

Paramagnetic centers in a solid-state environment usually give rise to inhomogeneously broadened electron paramagnetic resonance (EPR) lines, making conventionally detected free induction decay (FID) signals disappear within the spectrometer dead time. Here, high-resolution experimental results of an electrically detected FID of phosphorus donors in silicon epilayers with natural isotope composition are presented, showing Ramsey fringes within the first 150 ns. An analytical model is developed to account for the data obtained as well as for the results of analogous two-pulse echo experiments. The results of a numerical calculation are further presented to assess the capability of the method to study the exchange interaction between the donor spins and paramagnetic interface defect states. In the current samples, an upper limit of 5 MHz is obtained for the average exchange interaction.