Reduction of threading dislocations in crack-free AlGaN by using multiple thin SixAl1-xN interlayers

Crack-free AlGaN thin films were directly grown on SiC substrates by metalorganic vapor phase epitaxy, and their threading dislocation density was reduced by one order of magnitude using 1-2 nm thick, heavily Si-doped AlN multiple interlayers. The interlayers form SixAl1-xN ternary alloys, where the Si molar fraction ranges typically from 0.07 to 0.17. This technique enables us to grow crack-free AlGaN films, since the film thickness of about 1 mum is much smaller than that required in conventional epitaxial lateral overgrowth techniques. Both termination and looping of threading dislocations were observed near the interlayers using cross-sectional transmission electron microscopy. Light emitting devices with the SixAl1-xN multiple interlayers showed a remarkable improvement in the intensity and spectral width of electroluminescence and the series resistance. (C) 2003 American Institute of Physics.