INVESTIGATION OF INAS SINGLE QUANTUM-WELLS BURIED IN GAAS[001] USING GRAZING-INCIDENCE X-RAY-DIFFRACTION

InAs single quantum wells were grown by means of a low-pressure metal-organic chemical vapour deposition technique on GaAs[001]. Their nominal thickness was varied among 0.7, 2, 3 and 4 monolayers and they were buried under a thick GaAs top layer. The samples were investigated by means of the grazing incidence x-ray diffraction using the weak (200) in-plane reflection. Depth resolution was obtained setting the angle of incidence and exit alpha(i) and alpha(f), respectively, smaller or larger than the critical angle of total external reflection alpha(c). Owing to the high sensitivity near the surface the collected rod scans show pronounced thickness oscillations for alpha(i) > alpha(c). The thickness and the In-content, which control the scattering power of the single quantum wells were evaluated via simulation using the kinematic approach to x-ray diffraction. Partial relaxation occurs whenever the single quantum wells' thickness exceeds one monolayer. It is explained by the appearance of strain-reduced and non-tetragonally deformed islands built after the two- to three-dimensional transition of the growing mode.