Magnetic Field Effects on Carrier Transport
The domain of magnetic signals ranges from the very weak biomagnetic fields (∼ 10 fT) to the very high fields associated with superconducting coils (∼ 10 T) (see [1–6]). As a measure of the field strength H, we use the related magnetic induction B whose u
- PDF / 3,766,332 Bytes
- 36 Pages / 439.32 x 666.12 pts Page_size
- 9 Downloads / 248 Views
Magnetic Field Effects on Carrier Transport
The domain of magnetic signals ranges from the very weak biomagnetic fields (rv 10fT) to the very high fields associated with superconducting coils (rv 10 T) (see [1-6]). As a measure of the field strength H, we use the related magnetic induction B whose unit is 1 tesla = 1 Vs/m 2 and is related to the field strength as: B = JLoH in vacuum, where JLo is the free space permeability. In this very large span of over 15 orders of magnitude in field strength, the lower limit of field strengths « 1 IlT) requires relatively sophisticated detection devices and techniques [4], such as the flux-gate magnetometer, fiber optic magnetometer, nuclear magnetic resonance, and the superconducting quantum interference device, while the higher field strengths can be resolved by semiconductor magnetic sensors. Our discussion on the modeling issues will be restricted to the latter. Here, the signals are associated with geomagnetism (30-60IlT), magnetic (5storage media (rv 1 mT), permanent magnets for contactless sensing 100 mT), and current carrying conductors (rv 1 mT at 10 A) [6]. These signals lend themselves to two categories of direct and indirect applications [1-3]. Direct applications include measurement of the geomagnetic field, reading of magnetic storage media, identification of magnetic patterns in cards and banknotes, and control of magnetic apparatus. In indirect applications, a non-magnetic signal is detected via the magnetic field which is used as an intermediate carrier. Examples include voltage-free current detection and watt-hour meters, and contactless sensors, based on mechanical displacement of a permanent magnet, for detection of linear or angular displacement and velocity. Semiconductor magnetic sensors convert the magnetic signal into a useful electrical signal. Semiconductor magnetic sensors exploit galvanomagnetic effects due to the Lorentz force, vi!., F = -q(v x B) on mobile charge carriers. Here, q denotes the elementary charge and v the electron velocity. Note that while the field strength, H is the measurand, it is the magnetic induction, B that provides the sensor response; in semiconductors, the permeability JLrJLo rv JLo in the relation, B = JLrJLo H. Examples of A. Nathan et al., Microtransducer CAD © Springer-Verlag/Wien 1999
4 Magnetic Field Effects on Carrier Transport
105
semiconductor magnetic sensors include (see [6]): bulk, inversion layer, and heterojunction based Hall devices; bipolar junction magnetotransistors; magnetodiodes; carrier domain magnetometers; and magnetoresistors. This Section will, by and large, focus on simulation of Si magnetic sensors as they readily meet detection specifications for a large number of important applications in the range of IlT and higher. Most importantly, they can be batch fabricated at low cost using Si IC technologies and offer cointegration of signal correction and conditioning circuitry for increased functionality [1]. Indeed co-integration with circuitry has now become the driving force of current resea
Data Loading...
