An ultra-thin compliant sapphire membrane for the growth of less strained, less defective GaN

• Ultra-thin sapphire membrane micro-stripes were used as a compliant substrate.
• High quality GaN layer was grown on the sapphire membrane.
• Misfit dislocation density at the interface was reduced by 28%.
• Threading dislocation density in GaN was measured to be 2.4×108/cm2.
• Stress in GaN was reduced due to stress absorption by compliant sapphire membrane.

An ultra-thin (26 nm) sapphire (Al2O3) membrane was used as a compliant substrate for the growth of high quality GaN. The density of misfit dislocations per unit length at the interface between the GaN layer and the sapphire membrane was reduced by 28% compared to GaN on the conventional sapphire substrate. Threading dislocation density in GaN on the sapphire membrane was measured to be 2.4×108/cm2, which is lower than that for GaN on the conventional sapphire substrate (3.2×108/cm2). XRD and micro-Raman results verifed that the residual stress in GaN on the sapphire membrane was as low as 0.02 GPa due to stress absorption by the ultra-thin compliant sapphire membrane.