They can be used to detect magnetic fields and their changes, and can be used in a variety of magnetic field-related applications. Hall elements have many advantages. They have a solid structure, small size, light weight, long life, easy installation, low power consumption, high frequency up to 1MHZ , vibration resistance, and are not afraid of dust, oil, water vapor, and salt spray.
Contamination or corrosion. Hall devices with various compensation and protection measures have a wide operating temperature range. The so-called Hall effect refers to a physical phenomenon in which a lateral potential difference occurs when a magnetic field acts on a carrier in a current-carrying metal conductor or a semiconductor. The Hall effect of metals was discovered by American physicist Hall in The experimental evidences lead us to draw the following scenario, depicted in Fig.
Metals with high work-functions form a Schottky contact with the semiconductor. As a Schottky contact is made, electrons in the conduction band of the semiconductor have a higher energy than electrons in the metal. As a consequence, they tunnel into the metal leaving uncompensated positive charge in the semiconductor. At equilibrium, the built-in potential V bi prevents additional electrons to migrate. This equilibrium corresponds to the alignment of the Fermi levels.
When light is shed, if the light penetration depth through the metal is longer than the film thickness, photons can be absorbed and electron-hole pairs are generated A hole can readily be neutralized by an electron transferred from the metal but an electron cannot easily overcome the barrier or flow through the highly-resistive, intrinsic semiconductor.
Yet, an additional electron in the space charge region results in a lowering of the barrier height that can be modeled with the theory of image forces As the negative potential arising from the Coulomb force between electron and image charge decreases with the distance x from the interface, this results in a rounding of the net potential barrier as depicted in Fig.
If the semiconductor is highly resistive and photo-exited electrons cannot easily be discharged through it, which is the case here, the lowering of the Schottky barrier becomes significant, as reveled by the significant increase of the leakage current in reverse biased in Fig. In open-circuit conditions, as negative charge builds up, electrons with higher energy can cross the barrier. Electrons must acquire a substantial velocity for a large Hall voltage to appear on the edges of the metal.
The immediate foreseeable application for the system we have presented here is sensing of magnetic fields. Let us therefore compare our prototype device with commercial Hall sensors. First, standard Hall sensors require four contacts two for the bias current, two for the measured voltage whereas our sensor requires only two contacts.
The non-optimized system in Fig. In the former, attempts to bias at higher currents to increase sensitivity would make the linearity-error increase significantly if no heat sink is used. Our sensor has a linearity-error that is independent on sensitivity because no Joule heating is produced.
If cold light sources, such as white LEDs are employed, the temperature of the sensor would be unaffected by the light. Let us finally point out that the sensitivity of our system can be greatly increased in different ways. First, doping Si would increase the diffusion current, and therefore the sensitivity. The trade-off must be found by carrying out a systematic study with doping concentration. Another way to increase the sensitivity is to reduce the thickness of the metallic film.
A thinner film would be more transparent and more resistive, therefore the benefits would be two-fold. Replacing Si with a direct band-gap semiconductor, such as GaAs, should also increase sensitivity. The silicon wafers used in the experiment were purchased from Siltronix France. Metal targets were Metallic films were deposited on as-received silicon by d.
The slabs were partially masked to access the silicon surface. Electric contacts were made by aluminum wire bonding for the chips and epoxy for the slabs. The magnetic field was generated by a water-cooled electromagnet. No optical fiber was connected. The light intensity was measured by using a Newport digital power meter after removing all the filters from the sensor and multiplying by the ratio between the sample area and sensor area. Open circuit voltage and current-voltage characteristics were measured by using Keithley multimeters.
Hall, E. Tyler, W. Baibich, M. Binasch, G. Enhanced magnetoresistance in layered magnetic structures with antiferromagnetic interlayer exchange. B 39 , — Hurd, C. Work Function: Measurements and Results, edited by M.
Wunderlich, J. Spin-injection Hall effect in a planar photovoltaic cell. Oka, T. Photovoltaic Hall effect in graphene. B 79 , Heller, A. Rhoderick, E. Metal-semiconductor contacts , 2 nd ed. Oxford University Press, Quimby, R. Clicking on the Field Lines box will show the invisible magnetic forces at work and help you to visualize this. A similar effect is seen in semiconductors, where the Hall effect plays a large role in the design of integrated circuits on semiconductor chips.
In most conductors, such as metals, the Hall effect is very small because the density of conduction in electrons is very large and the drift speed charged particle erraticism is extremely small, even for the highest obtainable current densities.
The Hall effect is therefore considered unimportant in most electric circuits and devices and is not mentioned in many texts on electricity and magnetism. However, in semiconductors and in most laboratory plasmas, the current density is many orders of magnitude smaller than in metals, and the Hall effect is correspondingly larger and is often easily observable.
Some devices for measuring magnetic fields make use of semiconductors as the sensing elements and are called Hall probes. Interactive Tutorials. Last modified on 17 June
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