Features of the Surface Conductivity of Silicon Microstructures at Low Temperatures

Abstract

Research in the field of magnetoelectronics opens up the possibility of creating sensitive sensors of a magnetic field based on deluted semiconductors. On the other hand, the performance of devices in difficult operating conditions, namely at cryogenic temperatures, including the temperatures of liquefied helium, is no less difficult and an important problem. In this work, considerable attention is paid to establishing the relationship between magnetic and magneto-trasport properties of silicon microcrystals doped by boron to concentrations in the vicinity of the metal-dielectric phase transition, which is important in the development of magnetic field sensors, spin valves, etc. The peculiarities of transferring charge carriers of silicon microcrystals to doped boron to concentrations corresponding to the transition of metal-dielectric and nickel, located in the near-surface area of he crystal, are investigated. The magnetization of up to 0,4 Т and the magnetoresistance of filamentous microcrystals of silicon under the action of magnetic fields up to 14 T for temperatures of 4.2 K were studied. A detailed analysis of the results of theoretical studies of magnetic and magnetic transport properties Si <B, Ni> was carried out. The quadratic nature of the dependence of the negative magnetoresistance on the magnetization in silicon microcrystals is established for the magnetization exceeding 5 ∙ 105 A / m. However, for small M up 5∙105 A/m, the quadratic dependence of the magnetoresistance on the magnetization is violated, which is connected with the hopping mechanism of carrier transport over one occupied impurity levels. The coefficient of proportionality between the magnetoresistance and the magnetization of the crystals increases if the impurity concentration increases, approaching the transition of the metal-dielectric, and the temperature becomes lower. The maximum value of the negative magnetoresistance coefficient for the investigated filamentary samples Si <B, Ni> is about 10%, corresponding to the magnetization of the sample, equal to 6.53 ∙10^ 5 A/m. It was established that the basis of the low-temperature transfer of charge carriers for silicon microcrystals doped by a boron impurity to the concentration corresponding to the transition of a metal dielectric and a magnetic impurity is the polarization hopping conductivity. The large magnitudes of the negative magnetoresistance correspond to the hopping conductivity of charge carriers by twice occupied admixture states. It was established that the introduction of a magnetic impurity could affect the electromagnetic properties of the crystal associated with the transport of charge carriers by hopping tunneling in the near-surface zone. The results of low-temperature properties of silicon microcrystals doped with boron and nickel can form the basis of the development of sensitive sensors of a magnetic field with a thermoresistive principle of operation, including multifunctional sensors.Ref. 30, fig. 5, tabl. 1.