We present a structural investigation of self-assembled InGaAs quantum dots on GaAs(001) substrates grown by molecular-beam epitaxy. The grazing incidence X-ray scattering measurements were performed at BL17B of Taiwan Light Source and BL12B2 of SPring-8. The strain field, composition distribution, and shape of the dots are determined. We found that In concentration was less than the nominal composition, 50% near the dot/substrate interface and exceeded 50% near the top of the dots, indicating In surface segregation. In addition, the relation between the strain and the composition did not obey Vegard's law.
- Quantum dots
- X-ray scattering