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(Color online) AFM images of InAs NW’s. (a) (sample A) and with InGaAs thickness (b) (sample B), (c) (sample C), and (d) , grown under larger overpressure (sample D). The heights and NW’s densities depend on growth condition and thickness of the InGaAs buffer layers. However, samples A and D (B and C) show similar height distributions.
High resolution TEM [dark field for ] cross section images of NW’s. Bright and dark regions in InGaAs show typical mass contrast associated with compositional modulation in samples (a) B, (b) C, and (c) D.
(Color online) Strain and Ga concentration profiles obtained from GIXD for samples A, B, and D. (a) Strain relaxation along the height of the NW for the  and directions. (b) Ga concentration profile for the direction for samples B and D, normalized to the maximum Ga concentration from the InGaAs buffer layer (considered as 100%). The curves for are very similar. The inset shows the radial scans for InAs taken at both energies. The Ga concentration for sample B, shown in (b), was considered for strain calculations as well. The dashed curve for sample B in (a) was obtained assuming a Vegard law correction.
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