Incorporation of the transition metal Hf into GaN |
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Authors: | Bartels J Freitag K Marques JG Soares JC Vianden R |
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Institution: | (1) Institut für Strahlen- und Kernphysik, University of Bonn, D-53115 Bonn, Germany;(2) Centro de Fisica Nuclear, University of Lisbon, Lisbon, Portugal |
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Abstract: | The perturbed angular correlation (PAC) technique was applied to study the incorporation of the transition metal Hf into GaN
after implantation. To this end the PAC probe 181Hf(181Ta) was implanted into epitaxial Wurtzite GaN layers (1.3 μm on sapphire) with an energy of 160 keV and doses of 7× 1012 at/cm2. PAC spectra were recorded during an isochronal annealing programme, using rapid thermal annealing (RTA) and furnace annealing,
in the 300–1000oC temperature range. After implantation the spectra show a damped oscillation corresponding to a quadrupole
interaction frequency (QIF) of νQ= 340 MHz for 30% of the probe nuclei. Annealing up to 600oC reduces the damping of this frequency without an increase of
the probe atom fraction fs in these sites. Above 600oC fs grows rapidly until after the 900oC RTA step more than 80% of the Hf probes experience a well defined QIF due to the incorporation
of Hf on undisturbed sites of the hexagonal GaN wurtzite lattice. An interaction frequency of νQ= 340 MHz is derived. RTA and furnace annealing yield similar results for annealing up to 800oC, where the undisturbed fraction
reaches about 60%. Then RTA at higher temperatures increases this fraction, while furnace annealing leads to a decrease down
to 22% after annealing at 1000oC. To our knowledge this is the first time that a transition metal probe like Hf is incorporated
to such a large extent into a semiconductor lattice.
This revised version was published online in August 2006 with corrections to the Cover Date. |
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