Role of relative tilt on the structural properties of GaInSb epitaxial layers grown on (001) GaSb substrates

The extent of relative tilt angle, crystalline quality, and relaxation of G axIn1-xSb layers grown on (001) GaSb substrates by organometallic vapor pha se epitaxy have been investigated, using double-crystal x-ray diffraction a nd transmission electron microscopy. An unexpectedly large tilt is formed b etween Ga0.8In0.2Sb epitaxial layers and oriented (001) GaSb substrates whi ch has not been previously reported. Double-crystal x-ray diffraction measu rements revealed that the tilt angle between the Ga0.8In0.2Sb epilayers and the substrates increases as the layer thickness increases. A strong correl ation has been established between the variation of the tilt angle and the residual strain in the layers. Transmission electron micrographs of Ga0.8In 0.2Sb layers revealed that irregular dislocation activities occur in the la yer at different distances from the interface which could be related to til t formation and relaxation. The structural characteristics of the layers as a function of the compositional variation showed that the amount of tilt a ngle is small when the indium concentration was in the range from 0 to 12%, but increases at higher indium concentrations. Ga1-xInxSb layers with poor crystalline quality and small tilt angle are obtained when the indium conc entration was more than 25%. The tilt angle between Ga0.8In0.2Sb epilayers and GaSb substrates grown at temperatures ranging from 560 to 620 degrees C was essentially identical, indicating that the tilt formation is not a kin etic effect. (C) 1999 American Institute of Physics. [S0021-8979(99)05414-6 ].