The beginning of the space-age in the 1950s led to interest in the effects of radiation on semiconductors. The systematic investigation of defect centres in semiconductors began in earnest over 30 years ago. In addition to defect identification, information was also obtained on energy-level structures and defect migration properties. When designing electronic systems for operation in a radiation environment, ~tis imperative to know the effect of radiation on the properties of electronic components and materials comprising these systems. In some instances, the effects of irradiating electronic materials can be used to obtain desired material properties (mesa isolation, implantation, etc.). However, when electronic devices are exposed to radiation, defects may be introduced into the material. Depending on the application, these defects may have a detrimental effect on the performance of such a device. For this study, the semiconductor gallium arsenide (GaAs) was used and the defects were introduced by electrons, alpha-particles, protons, neutrons and argon sputtering. These particles were generated using radio-nuclides, a high-energy neutron source, a 2.5 MV Van de Graaff accelerator and a sputter gun. The influence of particle irradiation on the device properties of Schottky barrier diodes (SBDs) fabricated on GaAs is presented. These device properties were monitored using a variable temperature current-voltage (I-V) and capacitance-voltage (C-V) apparatus. In order to have an understanding of the change in electrical properties of these contacts after irradiation, it is necessary to characterize the radiation-induced defects. Deep level transient spectroscopy (DLTS) was used to characterise the defects in terms of their DLTS "signature", defect concentration, field enhanced emission, and thermodynamic properties. / Thesis (PhD)--University of Pretoria, 1994. / gm2014 / Physics / unrestricted