Study of the Photovoltage in Mn/SiO₂/n-Si MOS Structure at Cryogenic Temperatures

Lateral photovoltaic effect in metal/insulator/semiconductor hybrid structures is a significant phenomenon for spintronics, as it establishes the interplay between the optical irradiation, electronic transport and spin-dependent properties of carriers. In present work we investigated photovoltaic phenomena in Mn/SiO₂/n-Si MOS structure. The sample was prepared on a single-crystal n-Si (phosphorus-doped) substrate. The SiO₂ layer with thickness of 1.5 nm was formed on the substrate surface by a chemical method. Manganese film with thickness of 15nm was deposited by thermal evaporation in ultrahigh vacuum in the “Angara” chamber. It was observed that at T < 45 K the values of lateral and transversal photovoltage non-monotonically depend on the temperature and such dependences show complex behavior. Features of the photovoltage dependence on temperature, in the region above 20 K are explained by the change of carriers’ mobility and the competition between carriers’ drift velocity in the electric field of the space-charge region and their diffusion rate in the transverse and lateral directions. Below 20 K, the main contribution into the photovoltage is given by hot electrons injected from surface states levels to the conduction band. A strong magnetic field influence on the photovoltage below 20 K was observed. We associate it with the Lorenz force effect on the hot electrons, although we also don’t exclude the presence of mechanisms caused by spin-dependent scattering and recombination of hot electrons at occupied donor states.