Spin related effect in Terahertz photovoltaic response of Si-MOSFETs

We report on investigations of photovoltaic response of Si-MOSFETs subjected to Terahertz radiation in high magnetic fields. The MOSFETs develop a dc drain-to-source voltage that shows singularities in magnetic fields corresponding to paramagnetic resonance conditions. These singularities are investigated as a function of incident frequency, temperature and two-dimensional carrier density. We tentatively attribute these resonances to spin transitions of the electrons bounded to Si dopants and discuss the possible physical mechanism of the photovoltaic signal generation.