Asymmetric distribution of microtwins in a GaAs/Si heterostructure grown by molecular beam epitaxy

The distribution of microtwins in GaAs epilayer grown on Si (001) substrates tilted towards the [1̄11] direction by molecular beam epitaxy has been studied by transmission electron microscopy. An asymmetric distribution of microtwins attributed to substrate misorientation and two-dimensional (2D) growth mode has been found. Orthogonal [1̄10] and [110] cross sections are identified by the angle of tilt in large-angle convergent beam electron diffraction Tanaka patterns [J. Electron. Microsc. 29, 408 (1980)] taken across the GaAs/Si interface. It is found that (11̄1) microtwins are preferentially grown in GaAs epilayers on a tilted Si (001) substrate where the growth mode is 2D, while symmetrical (1̄1̄1) and (111) twins are observed when there is a reversal of twin distribution and the growth mode is 3D.