Second harmonic spectroscopy of semiconductor nanostructures

Semiconductor nanostructures and their application to optoelectronic devices have attracted much attention recently. Lower-dimensional structures, and in particular quantum dots, are highly anisotropic resulting in broken symmetry as compared to their bulk counterparts. This is not only reflected in highly anisotropic linear polarization properties, as studied recently in pyramide-shaped self-assembled InGaAs quantum dots, but also in second harmonic generation (SHG), which can be greatly enhanced allowing for detailed studies of such structures. SHG has contributed considerably as a technique to investigate solid state systems where the local inversion symmetry is broken by e.g. a surface or an interface, defect states or simply by structures so small that the bulk symmetry properties no longer are valid. Our idea is to use SHG in the configurations, where the bulk and surface contributions are forbidden for a homogeneous sample, so that the only source of SHG is associated with nanostructures embedded in the host material.