RADIATIVE AND MAGNETICALLY STIMULATED CHANGE OF THE ELECTRICAL PROPERTIES OF THE SiO2-Si STRUCTURE WITH A HIGH CONTENT OF DISLOCATION COMPLEXES

Abstract

The effect of various types of irradiation and magnetic field on the surface of the semiconductor is a relevant topic, since it is the change in the density of the SS that is responsible for the occurrence of sensitive (sensory) effects associated with dislocations adsorbed particles. The paper examines the effect of X-irradiation on the Si surface with different dislocation density (10 2 – 10 5 cm -2 ). The capacitance–voltage characteristics (CVC) of the Bi-SiO 2 -Si-Al structure indicate (their maxima) a sufficiently large charge in the dielectric layer of the capacity of this maximum. As the dislocation density increases, the capacitance value in the region of positive voltages decreases, which is associated with a decrease in the spatial charge region (SCR) value, as well as the distribution of the density of surface states in the band gap and their rate of recharging changes. To determine the density of surface states, the ideal (mathematically calculated) structures of Bi-SiO 2 -Si-Al (MOS) is compared with the real one. It is shown that the maximum concentration of SS is formed in the defect layers of the transition region, in which there are maximum mechanical stresses. The source of such stresses can be dislocations, which contribute to the energy spectrum of the surface. They increase the concentration of surface states in the depicted silicon zone by an order of magnitude. The spectrum becomes more complex with well-defined maxima in the energy range [from -0.1 to +0.4] eV at N ~ 10 5 cm -2 . This is due to the fact that, with low-energy irradiation of barrier structures in silicon oxide, the process of generation of electron-hole pairs occurs. The mobility of electrons in SiO 2 is much higher than the mobility of holes. Electrons that do not recombine leave the dielectric, holes (p + ) thermalize and fall to levels near the ceiling of the valence band. Thermal excitation of holes causes their capture at the level of tight bonds with a disturbance of equilibrium and the movement of atoms from the local to the free energy minimum. At the same time, the reaction takes place: ≡Si-O-Si≡ + p + →Si + +O 0 -Si≡ it shows the formation of "trivalent" silicon and "non-bridging" oxygen, which lead to the emergence of pseudovacancies, which lead to the accumulation of an additional charge in SiO 2 when the silicon structure is irradiated. In this case, the increase in the dislocation density enhances the effect of the radiation-stimulated SS change at the SiO 2 -Si interface. Under the action of X-irradiation on the surface of Si, there is a rearrangement of existing metastable defects and the formation of new ones, the increase in the density of which is associated with heterogeneity them from the volume semiconductor to the surface. They make a significant contribution to the SS spectrum. Upon irradiation, they can reorganize into more complex complexes with a change in SS. As a result of aging the structure Bi-SiO 2 -Si-Al in a magnetic field (MF) (B = 0.17 T) with different dislocation concentrations (terms of 4, 12, 20 days), the SS spectrum changes significantly. At N ≈ 10 4 – 10 5 cm -2 becomes monotonous after 20 days. The effect of a magnetic field on silicon does not cause the generation of electrically active defects in the near-surface layers of semiconductor, but promotes the rearrangement of oxygen and hydrogen complexes adsorbed on the surface, which are present on Si. It is they who determine the nature of the change in the SS due to the actions of the MF. Under the action of a magnetic field, a spin-dependent process of breaking chemical bonds in nanoclusters of structural defects (Si-H, Si-OH, -OH) occurs. As a result of breaking chemical bonds, hydrogen ions diffuse across the crystal and passivate acceptor and donor bonds. In addition, the action of MF leads to dynamic polarization of the nuclei of the Si 29 isotope atom and polarization of the electron spins in Si to the electron spins of oxygen due to the ultrathin interaction with polarized nuclei. A change in the orientation of the electron spin leads to the breakdown of the chemical bond. The effect of MF detection on non-magnetic materials, which are non-magnetic, is enhanced by prolonged exposure of samples to MF and the presence of defects in the near-surface layers. It is obvious that the presence of a dislocation will strengthen the influence of the MF on the change of the SS at the boundary SiO 2 -Si. Key words : silicon, magnetic field, X-irradiation, dislocations.