Control of polarization and dipole moment in low-dimensional semiconductor nanostructures

This work demonstrates the control of polarization and dipole moment in semiconductor nanostructures through nanoscale engineering of shape and composition. Rodlike (columnar) quantum dot (CQD) nanostructures, elongated along the growth direction, are obtained by molecular beam epitaxial growth. By varying the aspect ratio and the compositional contrast between the rod and the surrounding matrix, the polarization of the dominant interband transition is rotated from transverse-electric (TE) to transverse-magnetic (TM), and the dipole moment is modified — producing a radical change in the voltage dependence of absorption spectra. These results open the way toward optimization of quantum dot optical amplifiers and electro-optical modulators.

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