Absiraci-Noveldual-base, dual-collector, lateral transistors operating in the presence of dc and ac magnetic fields, demonstrate that the differential current at the collector is the result of emitter injection modulation and not carrier deflection. An understanding of basic operating principles has resulted in the design of optimized lateral-and vertical-injecting transitor configurations. The latter exhibit voltage sensitivities exceeding 20 V/T for NPN silicon, at room temperature, and a signal-to-noise ratio of 10s for a 1 T magnetic field. A frequency response in excess of 50 MHz should be possible for load resistances less than loo0 ohms.
A new semiconductor device for sensing uniaxial magnetic fields has been realized. The device is basically a dualcollector open-base lateral bipolar transistor operating in the avalanche region, and is referred to as a Magnetic Avalanche Transistor. It exhibits high magnetic transduction sensitivity compared to traditional Hall-effect and conventional nonlinear magnetoresistive devices. Several hundred experimental devices have been designed, fabricated, and tested over the past two years. Many structural and some process parameters were varied. The magnetic sensitivity of a typical device was found to be proportional to substrate resistivity. A sensitivity of 30 volts per tesla was measured for devices which used 5-ohm-cm p-type .substrates. The output signal measured between collectors is differential and responds linearly with field magnitude and polarity. A typical signal-to-noise ratio is 20 000 per tesla. The bandwidth is known to extend well beyond 5 MHz. The sensitive area is calculated to be on the order of 5 fim^. This communication describes the basic structure, fabrication, and characteristics for the magnetic avalanche transistor.
IntroductionThis communication reports on a new solid state magnetic-sensing device referred to as the Magnetic Avalanche Transistor (MAT). Basically this device is a dualcollector open-base lateral bipolar transistor which operates in the avalanche region. The magnetic field sensitivity of the device is high compared to the Hall-efFect and magnetoresistive sensors. The sensitivity of the device to a magnetic field is strongly related to its static I-V characteristics.
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