Fabrication of free-standing GaN substrates using electrochemically formed porous separation layers

We have developed a pore-assisted separation (PAS) method for the fabrication of free-standing GaN substrates, where bulk GaN crystals were separated from seed GaN templates at electrochemically formed porous layers. The pore size was controlled by the electrochemical process conditions and must be greater than 100 nm to realize separation within whole wafers. A 2-inch free-standing GaN substrate having a low dislocation density of 2.7×106 cm−2 was realized by growth of an 800-μm-thick GaN layer on the porous GaN template. A 3-inch free-standing GaN substrate was also fabricated by the PAS method, indicating its good scalability.