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RBS spectra for as grown (dashed) and 20 s RTA (solid). The simulated Ga and As contributions to the spectra are shown for the as grown sample. The RTA resulted in a reduction in As in the surface region and an overall reduction in film thickness.
XRD patterns from a film after successive RTA treatments at increasing temperature for 20 s each, with GaAs and GaN standards. The GaAs:N (111) and GaN:As (0002) peak positions indicate phase segregation of the amorphous ternary alloy into the corresponding binary crystalline phases.
SAD patterns for a- as grown (a); after 20 s RTA (b), and after 20 s RTA taken close to the interface (c) (black spots from substrate). Note the strong dotted pattern within the second ring due to (0002) GaN planes. (d) Cross-section of the film showing the formation of randomly distributed grains. (e) High resolution image showing formation of GaAs (larger lattice spacings) and GaN (smaller lattice spacings) crystals. (f) Z-contrast microscopy image of a GaAs grain (brighter contrast from heavier As atoms). Note twinning within the GaAs crystals in (e) and (f).
Absorption spectra from as grown and 20 s RTA . The shift in the band edge indicates the formation of a higher band gap phase.
A comparison of the interplanar distances measured by SAD and XRD for after 20 s RTA with the calculated power diffraction data from GaAs and GaN. The double arrow indicates one broad ring measured from the inner diameter, the strongly dotted pattern, and the outer diameter.
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