Nature and origin of V-defects present in metalorganic vapor phase epitaxy-grown (In_xAl_(1-x))N layers as a function of InN content, layer thickness and growth parameters

摘要

Our study of samples grown in different metalorganic chemical vapor deposition reactors and with different growth conditions reveals that V-pits are always present in (In_xAl_(1-x))N films whatever the layer thickness and the InN content. V-pits are empty inverted pyramids terminating threading dislocations. InN-rich triangular regions are present around the threading dislocations terminated by pits with a hexagonal 6-fold symmetry distribution in {11 -20} planes. The nature of the facets of the V-pits depends on the growth conditions: pits with either {11-2l},l being between 1 and 3, or {1-101} facets have been observed. Moreover, the nature of the threading dislocations terminated by pits also depends on the growth conditions. Our observations suggest that with a high V/III ratio only edge α+c-type dislocations are terminated by pits whereas with a low V/III ratio both edge α-type and mixed a+c-type dislocations are terminated by pits.