Papers by Keyword: Hall-Effect

Abstract: This work takes into account low Al implanted concentrations of 3 x 10¹⁸ cm^-3 and 1 x 10¹⁹ cm^-3 to compare the results of 1600°C and 1950°C post-implantation annealing treatments, done with two different annealing times per given implanted Al concentration and post implantation annealing temperature. Current-voltage and Hall effect measurements were performed to have the drift hole density and the drift hole mobility curves in the temperature range 100 - 650 K. The fitting of these curves in the frame of a carrier transport into the extended states of the valence band were performed to estimate the Al acceptor density, the donor compensator density, and the Al acceptor ionization energy. Peculiar feature of hole density and hole mobility curves is a contemporaneous increase of both carrier density and mobility values with increasing annealing time, which is congruent with the output parameters of the fitting procedure. The latter shows an almost stable Al electrical activation and a decrease of compensation with increasing annealing time for constant annealing temperature and given implanted Al concentration.

Abstract: In an electric power steering (EPS) system, it is important to make a precise and reliable measurement of the torque on the steering wheel. A non-contact torque sensor has been developed for EPS system. The sensor is based on a magnetic principle that the magnetic flux path is changed with the torsion of a torsion bar which is placed in the steering shaft. The change of magnetic flux density in the working airgap is detected by a standard Hall-effect IC. The sensor has broad prospects for its good performance, simple structure and low cost. This paper introduces the torque sensor’s working principle, analyzes the magnetic circuit by 3D simulation, and concludes its key technologies and development trends.

Abstract: Aluminum ions (Al+) were implanted at room temperature or at 500°C into n-type 4HSiC. The implantation damage (displaced Si atoms) and the electrical activation of Al+ ions (concentration of Al acceptors) were determined by Rutherford backscattering in channeling mode and Hall effect, respectively, as a function of the annealing temperature.

Abstract: The thin films of SiO and SiON were deposited individually by the inclination opposite target type DC magnetron sputtering equipment onto the glass substrate. And it was deposited IZO(In2O3 (90wt.%) + ZnO(10wt.%)) on those films. The effects of SiO and SiON were investigated on properties of IZO thin films. AFM images of IZO thin film included SiON film were shown smoother surfaces than that included SiO film. Multi layers of IZO were shown good properties because it have high transmissivity. Resistivity is in inverse proportion to Mobility. If it deposited SiO and SiON, generate layer of change between two layers(SiO or SiON + Substrate). Layer of change influenced resistance because Oxygen content was more than single layer of IZO. In case of using PET substrate, it influenced stronger than Glass substrate for rigid gas permeable and osmosis.

Abstract: We report on investigation of p-type doped, SiC wafers grown by the Modified- Physical Vapor Transport (M-PVT) method. SIMS measurements give Al concentrations in the range 1018 to 1020 cm-3, with weak Ti concentration but large N compensation. To measure the wafers’ resistivity, carrier concentration and mobility, temperature-dependant Hall effect measurements have been made in the range 100-850 K using the Van der Pauw method. The temperature dependence of the mobility suggests higher Al concentration, and higher compensation, than estimated from SIMS. Additional LTPL measurements show no evidence of additional impurities in the range of investigation, but suggest that the additional compensation may come from an increased concentration of non-radiative centers.

Abstract: 4H-SiC implanted with high dose of phosphorus has been shown to exhibit lower sheet resistance than 4H-SiC implanted with high dose of nitrogen. In this paper, we have implanted various doses (1x1014cm-2, 2x1014cm-2, 1x1015cm-2 and 4x1015cm-2) of phosphorus into 4H-SiC in order to extract the ionization energy of phosphorus in 4H-SiC as a function of the doping concentration. Variable temperature Hall effect measurements were performed in the temperature range from 60-600K. Least square fits using the charge neutrality equation with two donor levels were used to extract the ionization energies and donor concentrations from the measured data. The ionization energies for both, the hexagonal (53meV, 49meV and 26meV) and the cubic (109meV, 101meV and 74meV) site decreased as the donor concentration (5x1018cm-3, 9.8x1018cm-3 and 3.4x1019cm-3) increased.

Abstract: A variety of 4H-SiC samples from undoped crystals grown by the physical vapor transport technique have been studied by temperature dependent Hall effect, optical and thermal admittance spectroscopy and thermally stimulated current. In most samples studied the activation energies were in the range 0.9 - 1.6 eV expected for commercial grade HPSI 4H-SiC. However, in several samples from developmental crystals a previously unreported deep level at EC-0.55 ± 0.01 eV was observed. Thermal admittance spectroscopy detected one level with an energy of about 0.53 eV while optical admittance spectroscopy measurements resolved two levels at 0.56 and 0.64 eV. Thermally stimulated current measurements made to study compensated levels in the material detected several peaks at energies in the range 0.2 to 0.6 eV.

Abstract: We have succeeded to grow high quality phosphorus doped n-type diamond thin films on {111} diamond substrates. Although the ionization energy of phosphorus donor is large (0.57 eV), the n-type conductivity is clearly observed by Hall measurements. The Hall mobility is as high as 660 cm2/V-sec at room temperature. In this paper, current status of n-type diamond research are mentioned mainly focused on the growth of high mobility n-type diamond and its electrical properties. High quality diamond growth has been carried out by surface pre-treatment of diamond substrate. The Hall measurements performed in a wide temperature range gives detailed information about the n-type conductivity nature.

Abstract: The high sensitivity of the low temperature electrical properties of p-type pure tellurium (Te) to impurities, structural boundaries, point defects and dislocations allows to investigate the structural imperfection profiles in crystals grown under different conditions. Our interest was focused on studying the influence of grain boundaries on the electrical properties of the samples that were remelted and directionally solidified in space (µg) without a seed (W-µg), in comparison with the sample grown under the normal earth conditions (1g0) and a nanocluster sample obtained by filling with melted Te of dielectric opal matrix voids (Opal sample). The W-µg ingot of Te was prepared in the "Crystallizator" furnace under microgravity conditions aboard the "Mir" space station [1]. The concentration variation of electrically active defects and neutral defects along the samples were studied by galvanomagnetic methods (Hall effect and electrical resistivity) in a wide temperature range from 0.4 to 300 K. In these measurements, the following effects caused by the micro- and nano- crystalline structure were found: low hole mobility, high concentration of neutral defects, and anomalous positive magnetoresistance in low magnetic fields at low temperatures. Besides, the specific resistivity of the space sample was found to oscillate (up to 20%) along the length which can be correlated with the presence of a few contact points of the melt with the ampoule wall. This ingot was formed as a result of rapid homogeneous spontaneous solidification, accompanied by forming a micro-block structure. The appearance of the anomalous positive magnetoresistance was observed in the micro-block W- sample and the nanocluster Opal sample. It is a consequence of intensive hole scattering at the grain boundaries which leads to an increase of the intervalley transition probability and to a change of the spin sign of holes in a low symmetry Te crystal. According to the weak localization theory [2], the spin variation during the scattering results in a positive magnetoresistance of the sample in low magnetic fields, in contrast to bulk Te crystals.

Abstract: This paper reports on the degradation of inversion channel mobility of SiC MOSFET caused by the increase of channel doping. SiC MOSFETs were fabricated on three wafers, the doping concentrations of the epitaxial layer of which were 16 10 2× cm-3 (sample A), 17 10 2× cm-3 (sample B) and 17 10 4× cm-3 (sample C). The field effect mobility sharply decreases as the doping concentration increases. Hall mobility measurements have been done to investigate the degradation of the mobility due to doping. The measurement of sample A shows that, as a consequence of the decrease of the free carrier density due to MOS interface traps, the Hall mobility is as much as a factor of ten higher than the field effect mobility. In contrast, in regard to the measurement of sample B and sample C, we encountered unstable Hall voltage and could not obtain reproducible results. This implies that such high-density traps are generated that a channel disappears in the higher-doping samples.