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Clark, S., 1990. Comprehensive assessment of GaAs substrates for integrated circuit applications. PhD, Nottingham Trent University.
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Abstract
It is known that dislocations in GaAs substrates can affect the uniformity of the parameters of devices grown on them. It is thought that this is due to the influence of defects (such as EL2) which associate with dislocations. Efforts to improve substrate quality usually involve producing dislocation free material (by indium-doping), or alternatively, heat treating dislocated material to remove the-association of detects with dislocations.
In this work, dislocation structures, their associated precipitates and defect atmospheres are investigated by A/B etching; EL2 is investigated using its characteristic near-infrared absorption band; the electrical properties of the material are determined by Hall effect measurements: and some heat treated material is investigated by cathodoluminescence imaging. In addition, a new system for producing EL2 concentration ([EL2]) line-scans is described. This is based around a near-infrared silicon vidicon imaging apparatus, which images variations in EL2 using its characteristic absorption band.
New investigations of defects in indium-doped GaAs are detailed, with emphasis on those dislocations, and their associated defects, in the central region of the ingot. The effects of annealing on these defects is described and discussed.
Novel results of heat treatments followed by rapid cooling (quenching) on bulk material (large blocks) are described. Quenching from 1100°C, or above, produces superior uniformity to conventionally annealed material. However, [EL2] drops, dislocation density is increased and some samples display p-type conversion. After re-annealing quenched material at 950°G, [EL2] and semi- insulating nature are restored, without affecting the superior quenched uniformity.
Subsequently, an entire ingot was quenched from 1100°C and re-annealed at 950°C. This ingot quenched material was semi-insulating and displayed superior uniformity, although dislocation densities were high (at about 106cm-2). Initial processing results carried out on this material are promising, ingot quenching and re-annealing has great potential for providing uniform semi-insulating GaAs substrates.
| Item Type: | Thesis | ||||
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| Creators: | Clark, S. | ||||
| Date: | 1990 | ||||
| ISBN: | 9781369324112 | ||||
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| Divisions: | Schools > School of Science and Technology | ||||
| Record created by: | Linda Sullivan | ||||
| Date Added: | 10 Nov 2020 16:06 | ||||
| Last Modified: | 05 Oct 2023 10:06 | ||||
| URI: | https://irep.ntu.ac.uk/id/eprint/41597 |
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