Crack-free AlGaN thin films were grown directly onto SiC substrates by metalorganic vapor phase epitaxy, and their threading dislocation density was reduced by one order of magnitude using 1–2nm thick, heavily Si-doped AlN multiple interlayers. The interlayers formed SixAl1–xN ternary alloys, where the Si molar fraction ranges typically from 0.07 to 0.17. This technique permitted the growth of crack-free AlGaN films, since the film thickness of about 1µm was much smaller than that required in conventional epitaxial lateral overgrowth techniques. Both termination and looping of threading dislocations were observed near the interlayers by 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.

Reduction of Threading Dislocations in Crack-Free AlGaN by using Multiple Thin SixAl1–xN Interlayers. T.Akasaka, T.Nishida, Y.Taniyasu, M.Kasu, T.Makimoto, N.Kobayashi: Applied Physics Letters, 2003, 83[20], 4140-2