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Radiation Damage Characterization in Ar+ Implanted GaN
Published online by Cambridge University Press: 01 February 2011
Abstract
Damage microstructure evolution in GaN films implanted with argon ions (Ar+) as a function of implantation temperature was studied by cross-sectional transmission electron microscopy (TEM). After irradiation at room temperature, the implanted layer contained mostly isolated point defects. Implantation at elevated temperatures significantly reduced the number of isolated point defects. Numerous dislocations and regions exhibiting strain-contrast were observed after implantation at 300 °C. Bombardment at 600 °C resulted in formation of a new type of defect. Along with the partial dislocations and the strained regions, precipitates composed of carbon and nitrogen were identified by electron energy loss spectroscopy. These precipitates were formed in the vicinity of the Ar+ projected range where the amount of radiation damage was maximal. The high concentration of defects facilitated redistribution of carbon atoms introduced during the GaN film growth and resulted in the formation of precipitates. No precipitates were observed after implantation at 1000 °C. Consideration of the TEM results in conjunction with ion channeling data showed that presence of the precipitates correlated with a reverse annealing damage accumulation mode, which manifests itself as an increase of backscattering yield with increasing implantation temperature. The results of our study indicated that the carbon impurity in as-grown GaN films enhances the radiation damage accumulation rate and consequently has to be taken into account when ion implantation doping of GaN is performed.
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- Copyright © Materials Research Society 2004