IN situ 3D X-RAY reciprocal space mapping during lattice-mismatched InGaAs/GaAs growth

In situ three dimensional X-ray reciprocal space map (3D-RSM) measurement during InGaAs/GaAs(001) molecular beam epitaxial (MBE) growth is performed for the first time to investigate the anisotropies in relaxation processes along [110] and [110] direction caused by α and β misfit dislocations (MDs).The 3D-RSM is obtained by an X-ray diffractometer directly coupled to the MBE system in SPring-8. As the anisotropies, line dislocation densities and crystal qualities of both directions are simultaneously evaluated from position and broadness of 022 diffraction in the 3D-RSM, respectively. We demonstrated that 3D-RSM is a useful characterization technique to investigate anisotropies in dislocation behaviour and in relaxation processes, and believed that the fundamental knowledge obtained in this study will be important to design the metamorphic III-V solar cells with lower threading dislocation density.