Structural anisotropy and optical properties of InxGa1-xAs quantum dots onGaAs(001)

InAs and InxGa1-xAs (x = 0.2 and 0.5) self-organized quantum dots (QDs) wer e fabricated on GaAs(0 0 1) by molecular beam epitaxy (MBE) and characteriz ed by atomic force microscopy (AFM), transmission electron microscopy (TEM) , acid photoluminescence polarization spectrum (PLP). Both structural and o ptical properties of InxGa1-xAs QD layer are apparently different from thos e of InAs QD layer. AFM shows that InxGa1-xAs QDs tend to be aligned along the [1 (1) over bar 0] direction, while InAs QDs are distributed randomly. TEM demonstrates that there is strain modulation along [1 1 0] in the InxGa 1-xAs QD layers. PLP shows that In0.5Ga0.5As islands present optical anisot ropy along [1 1 0] and [1 (1) over bar 0] due to structural and strain fiel d anisotropy for the islands. (C) 2001 Elsevier Science B.V. All rights res erved.