Hillock formation and suppression on c-plane homoepitaxial GaN Layers grown by metalorganic vapor phase epitaxy

Hillocks on c  -plane homoepitaxial GaN epilayers were investigated. They were observed on epilayers grown on [11¯00] direction miscut free-standing GaN substrates with miscut angle not larger than 0.2° and were absent when substrate miscut angle increased to 0.4°. Atomic force microscopy (AFM) and cathodoluminescence measurements reveal a close correlation between hillocks and dislocation clusters, while hillocks are absent on layers grown on GaN substrate free of dislocation clusters. We believe that the hillocks originate from spiral growth around dislocation clusters. Larger strain induced by dislocation accumulation may be responsible for the hillock formation around dislocation clusters.

► This work presents formation of hillocks on c-plane homoepitaxial GaN vicinal surface.
► Different from previous works, hillocks were found to form around dislocation clusters other than single dislocation, while they are absent on GaN substrate free of dislocation cluster.
► The results reveal the formation mechanisms of hillocks on homoepitaxial GaN layers and can give a guide to substrate selection for device fabrication.