| Summary: | Copper is reported to diffuse at a high rate in GaAs (2.6 x 10⁻⁵ cm² s⁻¹ at 600°C). Dislocations and grain boundaries are expected to be preferential diffusion paths for copper diffusion at low temperatures. The present investigation was undertaken to establish to what extent preferential diffusion of Cu occurs along dislocations and grain boundaries in GaAs. The high diffusion rate enables observations to be made in reasonable times at low temperatures. A number of techniques including secondary ion mass spectroscopy, radioactive tracers, cathodoluminescence and photoluminescence were used to detect preferential diffusion.
The results do not indicate any preferential diffusion of Cu along dislocations or grain boundaries. Only a very small fraction of the Cu deposited on the surface diffused at a high diffusion rate. Copper reacted with the GaAs between 800°C and 1000°C producing a liquid on the top surface which solidified in complex Cu-Ga-As compounds. In addition, solute rich pipes were observed which extended from the top surface to the bottom of the wafer. No correlation between the position of the pipes and dislocation configuration was evident. === Applied Science, Faculty of === Materials Engineering, Department of === Graduate
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