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An Investigation of the Influence of Substrate Impurities on Ion Implanted GaAs MESFET Performance.

McIntyre, N. (1981) An Investigation of the Influence of Substrate Impurities on Ion Implanted GaAs MESFET Performance. Doctoral thesis, University of Surrey (United Kingdom)..

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Ion implantation is an alternative technique to the epitaxial growth of semiconductor material for device fabrication. In this work, Se+ ions have been implanted directly into bulk grown semi-insulating GaAs substrates to fabricate low noise MESFET devices. The device performance, when operated at dc and high frequencies, is shown to be dependent on the quality and technique and growth of the material. The basic principles of device operation have been outlined, followed by a review of previous studies of the assessment of GaAs and the influence of material and geometric parameters on device performance. Analysis of the different material types by secondary ion mass spectrometry has revealed high concentrations of donor impurities in the boat grown GaAs which have a significant influence on the ion implanted devices. In particular, large variations in saturation current, pinch off voltage and noise figure have been observed for materials implanted and fabricated under identical conditions. Cathodoluminescence has been used to gain further insight into the role of impurities in these materials and its potential as a technique for ingot selection assessed. The results have revealed the presence of acceptor impurities and native crystalline defect complexes, undetected by the chemical analysis which may account for some of the observed variations in material stability and device parameters. Measurements at the temperature of liquid helium have provided a further insight into the compensation mechanisms in the Cr doped and undoped semi insulating GaAs.

Item Type: Thesis (Doctoral)
Divisions : Theses
Authors : McIntyre, N.
Date : 1981
Additional Information : Thesis (Ph.D.)--University of Surrey (United Kingdom), 1981.
Depositing User : EPrints Services
Date Deposited : 06 May 2020 13:07
Last Modified : 06 May 2020 13:12

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