Tilt generation in step-graded InxGa1−xAs metamorphic pseudosubstrate on a singular GaAs substrate using a low-temperature grown InGaP interlayer

Metamorphic pseudosubstrates of In0.42Ga0.58As were grown by molecular beam epitaxy using step-graded InxGa1−xAs buffer layers grown either directly on a (001) GaAs substrate or on a GaAs substrate overgrown with a layer of low-temperature grown In0.51Ga0.49P (LT-InGaP). The structures were examined using x-ray reciprocal space mapping to determine the characteristics of the pseudosubstrates and buffer layers. For the sample grown on the LT-InGaP layer, the pseudosubstrate exhibited an asymmetric tilt around [11¯0] toward the [110] direction. Weak-beam dark-field electron imaging shows an imbalance of misfit dislocations with opposite sign Burgers vector. An explanation for this tilt is given and it is suggested that it may be responsible for the improved quality of epitaxial layers grown on such pseudosubstrates.