Warpage and stress relaxation of the transferred GaN LED epi-layer on electroplated Cu substrates

This study investigates the warpage and stress relaxation of a transferred GaN epi-layer on electroplated Cu substrates. Varying the electroplating current-density makes it possible to manipulate the crystallographic structure and hardness of the electroplated Cu substrate. A harder electroplated Cu substrate (with the (111) preferorientation) has less warpage and more stress relaxation in the transferred GaN wafer. An intrinsic compressive stress appeared in the electroplated Cu substrate, which helped to relieve the compressive stress of the transferred GaN epi-layer on the electroplated Cu substrate.