Infra-red emission from free carriers in silicon
Infra-red emission from free carriers in silicon
Previous publications have shown that beyond the band edge of silicon in the near infra-red the absorption coefficient depends on the carrier concentration in the material considered. These absorption coefficients are generally very small and therefore normal absorption measurement methods require very thick samples to obtain an appreciable absorption.A more sensitive emissivity technique is described which enables spatial carrier distributions in silicon to be determined directly in the device of interest. Both static sources (e.g. diffusions) and injected carriers have been investigated. Factors affecting the spatial resolution and ultimate sensitivity of the system are also considered.The emissivity technique is particularly useful for the observation of spatial variations in injected carrier concentrations and hence for diagnosing device faults. Carrier injection can occur across p-n junctions or externally, utilizing a laser probe. In the former case, current crowning and non-uniform injection have been observed in operating devices. Carriers may also be produced by illumination from a laser source. Observation of the subsequent infra-red emission enables the minority carrier lifetime and diffusion length to be determined. Employing this technique, spatial variations in lifetime and electrically active faults have been mapped.In an extension of this method, observation of charge fluctuations associated with reverse biassed p-n junctions have also been studied thus enabling point by point determination of the effective doping level within the depletion layer. This is an improvement on capacitance - voltage techniques which give a value averaged over the entire junction area.
University of Southampton
1977
White, John Charles
(1977)
Infra-red emission from free carriers in silicon.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
Previous publications have shown that beyond the band edge of silicon in the near infra-red the absorption coefficient depends on the carrier concentration in the material considered. These absorption coefficients are generally very small and therefore normal absorption measurement methods require very thick samples to obtain an appreciable absorption.A more sensitive emissivity technique is described which enables spatial carrier distributions in silicon to be determined directly in the device of interest. Both static sources (e.g. diffusions) and injected carriers have been investigated. Factors affecting the spatial resolution and ultimate sensitivity of the system are also considered.The emissivity technique is particularly useful for the observation of spatial variations in injected carrier concentrations and hence for diagnosing device faults. Carrier injection can occur across p-n junctions or externally, utilizing a laser probe. In the former case, current crowning and non-uniform injection have been observed in operating devices. Carriers may also be produced by illumination from a laser source. Observation of the subsequent infra-red emission enables the minority carrier lifetime and diffusion length to be determined. Employing this technique, spatial variations in lifetime and electrically active faults have been mapped.In an extension of this method, observation of charge fluctuations associated with reverse biassed p-n junctions have also been studied thus enabling point by point determination of the effective doping level within the depletion layer. This is an improvement on capacitance - voltage techniques which give a value averaged over the entire junction area.
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Published date: 1977
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Local EPrints ID: 467257
URI: http://eprints.soton.ac.uk/id/eprint/467257
PURE UUID: 0838b3e9-f1ab-4e6d-a91f-6518f89e3893
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Date deposited: 05 Jul 2022 08:17
Last modified: 05 Jul 2022 08:17
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Author:
John Charles White
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