High-quality 5cm' crack-free free-standing GaN was attained by hydride phase epitaxial growth on a Si-doped metalorganic vapor-phase epitaxial GaN template with a low dislocation density and subsequent laser-induced lift-off process. A low value of dislocation density of about 2.0 x 107/cm2 on the Ga-polar face was determined from cathodoluminescence images. X-ray diffraction and low-temperature photoluminescence were exploited to investigate the structural and optical properties of the GaN material. The full width at half maximum value of X-ray diffraction ω-scan of the free-standing GaN was 248arcsec for the (10▪4) reflection. The X-ray diffraction and low-temperature photoluminescence mapping measurements consistently proved the high crystalline quality as well as the lateral homogeneity and the small residual stress of the material. Hence, the bulk-like free-standing GaN studied here was highly advantageous for being used as a lattice-constant and thermal-expansion-coefficient matched substrate for additional strain-free homo-epitaxy of III-nitrides-based device heterostructures. The strain-free homo-epitaxy will significantly reduce the defect density and thus, an improvement of the device performance and lifetime could be achieved.

High-Quality 2'' Bulk-Like Free-Standing GaN Grown by Hydride Vapour Phase Epitaxy on a Si-doped Metal Organic Vapour Phase Epitaxial GaN Template with an Ultra Low Dislocation Density. D.Gogova, H.Larsson, A.Kasic, G.R.Yazdi, I.Ivanov, R.Yakimova, B.Monemar, E.Aujol, E.Frayssinet, J.P.Faurie, B.Beaumont, P.Gibart: Japanese Journal of Applied Physics, 2005, 44[3], 1181-5