@conference {12157,
	title = {Origin of Strain in GaN Thin Films},
	booktitle = {23rd International Conference on the Physics of Semiconductors},
	volume = {4},
	year = {1996},
	pages = {513},
	address = {Singapore},
	abstract = {<p>Photoluminescence measurements are used to determine the strain in GaN thin films grown by Molecular Beam Epitaxy. The strain which originates from growth on lattice mismatched substrates and from differences in thermal expansion coefficients is found to be greatly relaxed. Residual strains are shown to depend on the thickness of GaN buffer layers and the III/V flux ration during main layer growth. The results strongly suggest that the residual biaxial strain caused by the post-growth cooling can be modified by the incorporation of point defects during the main layer growth which introduce an additional hydrostatic strain field. The effect allows for strain engineering of GaN crystals.</p>},
	author = {Christian F. Kisielowski and Joachim Kr{\"u}ger and Michael S.H. Leung and Ralf Klockenbrink and Hiroaki Fujii and Tadeusz Suski and Sudhir G. Subramanya and Joel W. Ager III and Michael D. Rubin and Eicke R. Weber},
	editor = {Joachim Kr{\"u}ger}
}
@article {1849,
	title = {Strain Related Phenomena in GaN Thin Films},
	journal = {Physical Review B},
	volume = {54},
	number = {24},
	year = {1996},
	month = {12/1996},
	pages = {17745-17753},
	chapter = {17745},
	abstract = {<p>Photoluminescence (PL), Raman spectroscopy, and x-ray diffraction are employed to demonstrate the co-existence of a biaxial and a hydrostatic strain that can be present in GaN thin films. The biaxial strain originates from growth on lattice-mismatched substrates and from post-growth cooling. An additional hydrostatic strain is shown to be introduced by the presence of point defects. A consistent description of the experimental results is derived within the limits of the linear and isotropic elastic theory using a Poisson ratio nu =0.23+/-0.06 and a bulk modulus B=200+/-20 GPa. These isotropic elastic constants help to judge the validity of published anisotropic elastic constants that vary greatly. Calibration constants for strain-induced shifts of the near-band-edge PL lines with respect to the E<sub>2</sub> Raman mode are given for strain-free, biaxially strained, and hydrostatically contracted or expanded thin films. They allow us to extract differences between hydrostatic and biaxial stress components if present. In particular, we determine that a biaxial stress of one GPa would shift the near-band-edge PL lines by 27+/-2 meV and the E<sub>2</sub> Raman mode by 4.2+/-0.3 cm<sup>-1</sup> by use of the listed isotropic elastic constants. It is expected from the analyses that stoichiometric variations in the GaN thin films together with the design of specific buffer layers can be utilized to strain engineer the material to an extent that greatly exceeds the possibilities known from other semiconductor systems because of the largely different covalent radii of the Ga and the N atom.</p>},
	doi = {10.1103/PhysRevB.54.17745},
	author = {Christian F. Kisielowski and Joachim Kr{\"u}ger and Sergei Ruvimov and Tadeusz Suski and Joel W. Ager III and Erin C.  Jones and Zuzanna Liliental-Weber and Michael D. Rubin and Eicke R. Weber and Michael D. Bremser and Robert F. Davis},
	editor = {Joachim Kr{\"u}ger}
}
