Maciej Oszwaldowski

Two-dimensional (2D) planar version of the construction of an extraordinary magnetoresistance (EMR) based magnetic field sensor is proposed and verified in practice. The proposed 2D planar construction differs from the standard three-dimensional (3D) constructions by the position of the metallic shunt. In the new construction the metallic thin film of the shunt is coplanar with the sensitive semiconductor thin film. One of the advantages of that physically 2D planar construction is that it can be easily realized with the standard thin-film technology. Another advantage is that it is applicable to the preparation of EMR sensors based on the high mobility electron/hole gas confined in the new electronic materials like graphene and the topological insulator thin films both being physically 2D by nature. The validity of the planar construction is experimentally confirmed for model EMR sensors based on InSb/Ag thin films. Some interesting physical properties of those sensors are also described.

We report on the preparation of the first complete extreme temperature Hall sensor. This means that the extreme-temperature magnetic sensitive semiconductor structure is built-in an extreme-temperature package especially designed for that purpose. The working temperature range of the sensor extends from −270 °C to +300 °C. The extreme-temperature Hall-sensor active element is a heavily n-doped InSb layer epitaxially grown on GaAs. The magnetic sensitivity of the sensor is ca. 100 mV/T and its temperature coefficient is less than 0.04 %/K. This sensor may find applications in the car, aircraft, spacecraft, military and oil and gas industries.

We reinterpret the distribution of the Hall potential in the Hall bar-with-a-hole that has been found and interpreted by Mani and Klitzing [Appl. Phys. Lett., 64 1262 (1994)]. Our reinterpretation explains all the "paradoxes" without resorting to new theoretical conceptions.

The paper reports on the investigations of the weak localization (WL) effects in 3D polycrystalline thin films of InSb. The films are closely compensated showing the electron concentration n>10^{16} cm^{-3} at the total concentration of the donor and acceptor type structural defects >10^{18} cm^{-3}. Unless Pb-doped, the InSb films do not show any measurable or show very small WL effect at 4.2 K. The Pb-doping to the concentration of the order of 10^{18} cm^{-3} leads to pronounced WL effects below 7 K. In particular, a clearly manifested SO scattering is observed. From the comparison of the experimental data on temperature dependence of the magnetoresistivity and sample resistance with the WL theory, the temperature dependence of the phase destroying time is determined. The determination is performed by fitting theoretical terms obtained from Kawabata's theory to experimental data on magnetoresistance. It is concluded that the dephasing process is connected to three separate interaction processes. The first is due to the SO scatterings and is characterized by temperature-independent relaxation time. The second is associated with the electron-phonon interaction. The third dephasing process is characterized by independent on temperature relaxation time tau_c. This relaxation time is tentatively ascribed to inelastic scattering at extended structural defects, like grain boundaries. The resulting time dephasing time shows saturation in its temperature dependence. The temperature dependence of the resistance of the InSb films can be explained by the electron-electron interaction for T2 K.