Influence of the N-2/H-2 ratio on the structural features of InxGa1-xN/GaNfilms grown by MOCVD

The influence of the N-2/H-2 ratio in the growth environment on the defect structures of InGaN films was investigated by means of transmission electro n microscopy and atomic force microscopy. InxGa1-x N films (100 nm thick) w ere grown by MOCVD on GaN/Al2O3 (0001) epilayers. In one case, the InGaN fi lm was grown in pure H-2 carrier gas whereas, in the other, a N-2 + H-2 mix ture with a N-2/H-2 ratio of 4 was used. The actual indium incorporation in the InxGa1-xN epitaxial layers strongly depends on N-2/H-2 ratio. The surf aces of both InGaN films exhibit a high density ( similar to 10(9) cm(-2)) of hexagonal shaped pits with a diameter of the order of a few tens of nano metres. The defect structures observed in the samples are the same and seem to be mainly dislocations and inversion domains, which terminate on the fi lm surface with inverted hexagonal pyramids which are defined by six planes . (C) 2001 Elsevier Science B.V. All rights reserved.