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

摘要

High-quality 2″ crack-free free-standing GaN has been attained by hydride vapour phase epitaxial growth on a Si-doped MOVPE GaN template with a low dislocation density and subsequent laser-induced lift-off process. A low value of dislocation density of ～ 2.0 x 10~7 cm~(-2) on the Ga-polar face was determined from cathodoluminescence images. X-ray diffraction (XRD) and low-temperature photoluminescence (PL) were exploited to investigate the structural and optical properties of the GaN material. The full width at half maximum value of XRD ω-scan of the free-standing GaN is 248 arcsec for the (1014) reflection. The XRD and low-temperature PL 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 is highly advantageous for being used as a lattice-constant and thermal-expansion-coefficient matched substrate for additional strain-free homoepitaxy of Ⅲ-nitrides-based device heterostructures. The strain-free homoepitaxy will significantly reduce the defect density and thus, an improvement of the device performance and lifetime could be achieved.