Investigation of the structural and optical properties of free-standing GaN grown by HVPE

The potential of the high-growth rate hydride vapour phase epitaxy technique and laser lift-off for the fabrication of free-standing GaN substrates is explored. Structural and optical properties of 300 μm thick free-standing GaN have been investigated employing different analytical techniques. The x-ray diffraction (XRD) measurements prove good crystalline quality of the material grown. A comparatively low value of (3 ± 1) x 1016 cm-3 of Ga vacancy-related defects is inferred from positron annihilation spectroscopy data. Complete strain relaxation is observed on the Ga-polar face of the free-standing GaN by XRD and Raman spectroscopy measurements. The strain-free homoepitaxy will significantly reduce the defect density, and thus an improvement of the device performance and lifetime can be realized