An investigation of a circularly symmetric carrier domain magnetometer
An investigation of a circularly symmetric carrier domain magnetometer
The Carrier Domain Magnetometer is a circular p-n-p-n structure in which current is constrained to flow within a narrow region (domain). Application of a magnetic field normal to the plane of the device causes domain rotation at a frequency proportional to the magnetic flux density, provided this flux density is above a certain threshold level. The purpose of this work is to investigate the behaviour of the device, with particular emphasis on the threshold effect. The basic theory of domain formation is introduced, and this is followed by a detailed study of the dc behaviour of the device. A computer model is successfully developed to describe this dc behaviour. The dependence of domain rotation frequency and threshold on the device bias is investigated. Bias is found to affect the domain rotation frequency by altering the collector-base voltage of the intrinsic transistor. At low bias currents, domains become very diffuse, and this is shown to lead to high thresholds. A study of the operation of the device over a range of temperatures is presented, the results of which confirm existing theoretical analysis for the first time. Using a specially constructed magnetic prober, a systematic investigation of the threshold of a large number of devices is undertaken. This work reveals a strong correlation between misalignment of the npn emitter and base diffusion masks and device threshold, whereas other misalignments do not appear to be important. The effect of various contact geometries on device threshold is investigated experimentally, using the prober, and theoretically, by means of a computer model. A simple theoretical relationship between spatial variation of transistor gain and threshold is developed, which agrees well with experimental results. Finally the problems associated with the epitaxial device are discussed and various anomalous device characteristics are reported.
University of Southampton
1983
Lucas, David Rex Shirley
(1983)
An investigation of a circularly symmetric carrier domain magnetometer.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The Carrier Domain Magnetometer is a circular p-n-p-n structure in which current is constrained to flow within a narrow region (domain). Application of a magnetic field normal to the plane of the device causes domain rotation at a frequency proportional to the magnetic flux density, provided this flux density is above a certain threshold level. The purpose of this work is to investigate the behaviour of the device, with particular emphasis on the threshold effect. The basic theory of domain formation is introduced, and this is followed by a detailed study of the dc behaviour of the device. A computer model is successfully developed to describe this dc behaviour. The dependence of domain rotation frequency and threshold on the device bias is investigated. Bias is found to affect the domain rotation frequency by altering the collector-base voltage of the intrinsic transistor. At low bias currents, domains become very diffuse, and this is shown to lead to high thresholds. A study of the operation of the device over a range of temperatures is presented, the results of which confirm existing theoretical analysis for the first time. Using a specially constructed magnetic prober, a systematic investigation of the threshold of a large number of devices is undertaken. This work reveals a strong correlation between misalignment of the npn emitter and base diffusion masks and device threshold, whereas other misalignments do not appear to be important. The effect of various contact geometries on device threshold is investigated experimentally, using the prober, and theoretically, by means of a computer model. A simple theoretical relationship between spatial variation of transistor gain and threshold is developed, which agrees well with experimental results. Finally the problems associated with the epitaxial device are discussed and various anomalous device characteristics are reported.
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Published date: 1983
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Local EPrints ID: 460652
URI: http://eprints.soton.ac.uk/id/eprint/460652
PURE UUID: 647fa0af-bb91-4e26-9121-671b79c14eb1
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Date deposited: 04 Jul 2022 18:26
Last modified: 04 Jul 2022 18:26
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Author:
David Rex Shirley Lucas
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