Structural anisotropy and optical properties of In xGa 1− xAs quantum dots on GaAs(0 0 1)

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InAs and In x Ga 1− x As ( x=0.2 and 0.5) self-organized quantum dots (QDs) were fabricated on GaAs(0 0 1) by molecular beam epitaxy (MBE) and characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), and photoluminescence polarization spectrum (PLP). Both structural and optical properties of In x Ga 1− x As QD layer are apparently different from those of InAs QD layer. AFM shows that In x Ga 1− x As QDs tend to be aligned along the [1 1 ̄ 0] direction, while InAs QDs are distributed randomly. TEM demonstrates that there is strain modulation along [1 1 0] in the In x Ga 1− x As QD layers. PLP shows that In 0.5Ga 0.5As islands present optical anisotropy along [1 1 0] and [1 1 ̄ 0] due to structural and strain field anisotropy for the islands.