Manley, Martin Harold (1977) Semiconductor devices based on the carrier domain principle. University of Southampton, Doctoral Thesis.
Abstract
A programme of research has been carried out in order to investigate the viability of two novel types of bipolar semiconductor device based on the Carrier Domain principle: an analogue multiplier and a magnetometer. A carrier domain device consists of an elongated bipolar transistor within which emitter current injection is restricted to a small region, known as a domain. The domain can be moved in the device subject to an external signal, and so novel devices whose functions are directly governed by their geometry can be designed. The Carrier Domain principle and the basic design of the two devices investigated were suggested by B. Gilbert. Several different structures have been proposed for the implementation of the analogue multiplier. A series of computer programs has been developed by the author and used in a comparative study of these structures. Practical operation of a prototype carrier domain multiplier is described. The multiplication errors of the device have been measured, and the physical causes of these errors have been investigated. The prototype carrier domain multiplier has an X non-linearity of around 2% and a Y non-linearity of around 0.2% of full scale. A magnetic field sensor which utilizes the rotation of carrier domains in a circular semiconductor device subject to a magnetic field, has been made and operated-by the author. The device produces current pulses at a frequency proportional to the normal magnetic flux density for flux densities above a certain threshold level. The threshold effect has been investigated and shown to be due mainly to spatial variation of the pap transistor current gain. Other anomalous aspects of the device's operation, such as sensitivity to bias parameters and temperature, are described. The prototype device has a sensitivity of around 14KHz/tesla and operates down to 0.3 teals. An improved carrier domain magnetometer designed by the author is described. This device has a higher magnetic sensitivity (up to 200KHz/tesla) and operates down to approximately 0.1 tesla. The temperature sensitivity of the device's operation has been measured. A technique is described whereby small a.c. magnetic fields can be measured with the carrier domain magnetometer by using a steady magnetic field to bias the device above threshold.
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