Epitaxial growth of GaN on porous Si (111) substrate

The growth of GaN on porous (111) Si is studied by adjusting the depth and structure of the porous layer. It is shown that deep porous layer with high porosity on Si substrate can remarkably reduce cracks and improve crystal quality of the epitaxial GaN layer, while a shallow porous layer with low porosity causes vertical cracks across from the Si substrate to GaN layer. The porous substrate is beneficial to release the stress caused by their thermal mismatch.