Epitaxial growth and chemical lift-off of GaInN/GaN heterostructures on - and -sapphire substrates employing ZnO sacrificial templates
(Color online) XRD spectra measured from samples A and B, as well as their ZnO/sapphire substrates. (a) Sample A, off-axis scans from sample A aiming at , ZnO , and GaInN , respectively. (b) Sample B, off-axis scans from sample B aiming at (0006), ZnO , and GaN , respectively. The symmetries and the alignments in and provide clear evidence that the ZnO templates were epitaxially grown on - and -sapphire substrates and the GaInN/GaN heterostructures were epitaxially grown on the ZnO templates.
(Color online) Processing procedures for lifting-off GaInN/GaN structures from sapphire substrate, demonstrating a successful, crack-free lift-off.
(Color online) Morphologies recorded by Nomarski microscope from samples A and B before and after lift-off. (a) Sample A before lift-off. Sample A after lift-off. (b) Sample B before lift-off. Sample B after lift-off. The cracking lines are along the -direction of GaInN/GaN. The inset of shows the morphology of sample B after lift-off with a larger magnification.
(Color online) [(a) and (b)] Comparisons of XRD spectra measured, before and after lift-off, from samples A and B, respectively. [ and ] Comparisons of Raman-scattering spectra collected at room temperature, before and after lift-off, from samples A and B, respectively. The insets in and are the enlarged spectra of the first-order longitudinal optical modes observed in and , respectively. Redshift of in sample B is clearly observed after lift-off.
(Color online) High-resolution triple-axis XRD spectra measured from sample B before lift-off aiming at (a) , (b) , and (c) atomic planes. The bold curves are the Gaussian function fittings that illustrate the peak positions, as shown beside the peaks.
Lattice parameters of the GaN and ZnO layers extracted from the in-axis and off-axis and high-resolution XRD measurements using triaxis and skew configurations.
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