Evaluation of strain distribution in freestanding and buried lateral nanostructures

Article

关键词: X-RAY-DIFFRACTION;    GRAZING-INCIDENCE DIFFRACTION;    QUANTUM-WIRE STRUCTURES;    DIFFUSE-SCATTERING;    SURFACE GRATINGS;    ROUGH INTERFACES;    MULTILAYERS;   

DOI  :  10.1103/PhysRevB.60.16701

来源: SCIE

【 摘 要 】

A free-standing lateral nanostructure based on GaAs[001] containing a Ga0.97In0.03As single quantum well and similar structures after the overgrowth with GaAs and AlAs, respectively, have been investigated by high-resolution x-ray grazing incidence diffraction (GID) and conventional x-ray diffraction (HRXRD). The wire shape of the freestanding structure and the lateral density variation in the overgrown samples, were determined by running scans with constant length of the scattering vector (transverse scans) across the grating truncation rods (GTR's) close to the ((2) over bar 20) reflection. The in-plane strain distribution became available crossing the (220) GTR's by a scan in the longitudinal direction. Exploiting the capability of GID for depth resolution, the in-plane strain distribution was analyzed for different values of depth below the sample surface. The strain analysis was completed by HRXRD measurements close to the (001) reflection. The x-ray measurements were interpreted in terms of the distorted wave Born approximation applied for GID geometry. The strain distribution is determined by comparing the measured GTR intensities with the corresponding simulations containing the displacement fields obtained from finite-element calculations. At the freestanding wire structure we End laterally compressive strain of about Delta a/a(parallel to) = -2 X 10(-3) at the single quantum well (SQW) with a steep strain gradient close to the wire side walls. Both overgrown samples show pronounced lateral strain variation within the overgrown layer, which still appears up to the completely planar surface. Within the SQW the in-plane strain is still compressive after GaAs overgrowth and of similar amount compared to the freestanding grating. The strain is increased by about 30% after overgrowth with AlAs. For both overgrown samples the strain gradient near the wire side walls is reduced, but reaches a maximum close to the SQW. Accompanied by the defect passivation, these findings explain the difference in the energy shift of the photoluminescence line between freestanding and overgrown lateral nanostructures. [S0163-1829(99)08047-9].

【 授权许可】

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