Epitaxial growth and chemical lift-off of GaInN/GaN heterostructures on c- and r-sapphire substrates employing ZnO sacrificial templates

Abstract

The authors report epitaxial growth of GaInN/GaN heterostructures on ZnO/c-sapphire and ZnO/r-sapphire substrates by using metal-organic chemical-vapor deposition and chemical lift-off by etching away the ZnO templates. Using a black-wax technique and a vapor wax-elimination method, they demonstrate a 10×10 mm2 crack-free lift-off of GaInN/GaN from the c-sapphire substrate followed by bonding to a glass holder. On the ZnO/r-sapphire substrate, with the same lift-off processing, the GaInN/GaN was regularly cracked along its c-axis and the cracking is independent of the etching rate (controlled by the solution density). The cracking mechanism is investigated and discussed based on the x-ray diffraction and Raman-scattering characterizations before and after lift-off.