An investigation of minority carrier lifetimes in germanium and silicon semiconducting material has been undertaken.
A comparison of optical and electrical injection methods, as reported in the literature is given. An optical arrangement, including a coaxiallized spark gap system, is described.
Sample preparation is discussed with respect to surface treatments. A well etched surface (CP4 etched) reduces the surface effect to negligible proportions compared to the volume effect. However, a ground or sandblasted surface caused the surface term to be dominant.
The effects of constant current, photovoltaic effect at contacts, response time, and electrical field sweep-out of carriers are discussed.
A brief description of a suitable electrical injection circuit is given. Measured values of lifetime using this method are in good agreement with the optical measurements.
The volume lifetimes of n-type germanium were obtained for resistivities of 0.01, 5, 19, and 50 Ω-cm material. The lifetimes found at room temperature were <2 μs, 45 μs, 200 μs, and 175 μs respectively.
Both a 130 Ω-cm p-type silicon sample and an 8.2 Ω-cm n-type silicon sample displayed trapping effects at room temperature. A direct current light source, providing ambient background illumination, was found to eliminate the long decay component (>10⁻³ sec) for the p-type silicon only.
Germanium at 78°K showed a trapping effect similar to the silicon at room temperature.
A diffusion constant of 50 cm² /sec for holes in n-type material was used to establish a value for the surface recombination velocity of 2 x 10⁴ cm/sec for a ground surface. / Science, Faculty of / Physics and Astronomy, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/39446 |
| Date | January 1961 |
| Creators | Dyment, John Cameron |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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