Influence of the density of crack-initiating defects on crack spacing for GaN films on Si(111) substrate

This study examines the cracking of GaN films grown on Si(111) substrates, with particular focus on the effect of the density of crack-initiating defects (CIDs) on the crack spacing. The relationship between the CID density and crack spacing was examined by comparing specimens of the same thickness and under the same stress but with different CID density. The CID density in the GaN layer was changed by varying the ion-implanted area using patterning prior to metal-organic chemical vapor deposition (MOCVD) growth. The crack spacing decreased with increasing CID density, but this effect could not be explained by the previous model. Therefore, a CID-density related factor, n_d, was newly introduced to explain the crack spacing and film stress relationship.