Effect of the nucleation layer deposition temperature on the nature of defects in GSMBE GaN films

The microstructure of gas source molecular beam epitaxy GaN films deposited on (0001) sapphire is studied by transmission electron microscopy. For a nucleation layer deposited at 500 degrees C, high-quality materials, with only dislocations (density = 5 x 10(9) cm(-2)) in the volume of the film, are obtained. For a nucleation layer deposited at 550 degrees C, the resulting structural quality is poor. Inversion Domains and {11 (2) over bar 0} prismatic defects are observed. (C) 1999 Elsevier Science B.V. All rights reserved