Characterization of pit formation in III-nitrides grown by metalorganic chemical vapor deposition

Pit formation in III-nitride heterostructures such as InGaN/GaN and AlGaN/GaN grown by metalorganic chemical vapor deposition was characterized by transmission electron microscopy. The pit formation related with V defects has been reported in the InGaN/GaN multiple quantum well with high In composition [Appl. Phys. Lett. 79, 215 (2001)]. In this letter, we found that the mechanism of pit formation strongly depends on the indium and aluminum compositions in InxGa1-xN and AlxGa1-xN layers, respectively. By increasing the indium composition, the origin of pits is changed from the vertex of threading dislocations to the stacking mismatch boundaries induced by stacking faults and the three-dimensional island growth at the initial stage due to the large lattice mismatch, By increasing the, aluminum composition, the origin of the pits also varied from the surface undulation due to the elastic misfit strain to the vertex of threading dislocations. In addition, several inversion domains observed in III nitrides result in pit formation in the surface of films. (C) 2002 American Institute of Physics.