RBS Lattice Site Location and Damage Recovery Studies in GaN
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ITN, Sacavém, Portugal
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ISKP, University of Bonn, D-53115 Bonn, Germany, [email protected]
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Dept. Materials Science and Engineering, University of Florida, Gainesville, FL, USA Cite this article as: MRS Internet J. Nitride Semicond. Res. 4S1, G11.2 (1999)
Abstract Erbium was implanted with 160 keV at doses between 5x1014 and 5x1015 at/cm2 into (0001) epitaxial GaN on sapphire and annealed at various temperatures between 600° and 1000° C. The RBS/Channeling technique was used to analyze the damage recovery during different annealing steps and to determine the lattice location of the implanted Er. For a sample implanted with 5x1014 and annealed for 30 min at 600° C a complete overlap of the Er and Ga angular scans across the axis was observed, indicating that 100% of Er occupies substitutional sites. Measurements along the channel show that Er is located on Ga sites. The damage recovery was slightly better for the samples co-implanted with the same dose of Oxygen in an overlapping profile (E=25 keV). However, a complete recovery of the damage caused by the implantation was not achieved. Samples implanted with higher Er and O doses (5x1015 at/cm2 ) and at the same energies as above were annealed at 600° for 30 min and at 900°, 1000° C for 120 s using a proximity cap. The higher dose caused an almost complete amorphisation of the surface layer. After annealing indications of epitaxial regrowth were observed, however, the substitutional fraction remains substantially lower and the damage recovery is less complete.
Introduction GaN and other wide gap nitrides are materials with a large potential for high temperature electronics and optoelectronics applications. However, for the integration of GaN into circuits an adequate structuring technique is necessary. At present, the standard technique for selectively doping semiconductors and thus creating device structures is ion implantation. It unavoidably introduces damage to the crystal which has to be annealed in order to achieve electrically or optically active doping. Whereas in standard semiconductors like Si these procedures are well understood the situation in GaN is more complicated. The strong bonding of this material on one
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hand ensures a high resistance to lattice damage and amorphisation on the other hand it considerably hampers the epitaxial regrowth on the underlying undamaged crystal lattice after an implantation. It is therefore interesting to study the behavior of impurities after implantation as well as the general recovery of the GaN lattice. In the present study the lattice location of Er implanted in GaN and the possible influence of coimplanted Oxygen on the Er behavior was investigated. Doping of GaN with Er during growth or by implantation has been intensively studied mainly in photoluminescence mea
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