Optical anisotropy in InAs quantum dots formed on GaAs pyramids

In this paper, we present the results of polarization-dependent micro-photo luminescence (mu -PL) measurements of InAs quantum dots (QDs) selectively f ormed on GaAs pyramidal structures by selective area metalorganic vapor pha se epitaxy. Under nonresonant excitation, strong optical anisotropy is obse rved in the PL spectra of the InAs QDs. Under near-resonant excitation, whe re the excitation energy is close to the wetting layer luminescence, the li near polarization degree of InAs QD is larger than that observed under nonr esonant excitation. When excited and detected li-hts have the same polariza tion along two [110] directions, the PL is intense. However, in the cross p olarization configurations, the PL intensities are very weak. The observed strong optical anisotropy in InAs QDs formed on GaAs pyramids under nonreso nant excitation can be attributed mainly to the asymmetry of the QD potenti al which results from the anisotropic strain relaxation and shape of QDs, w hile that under the near-resonant excitation is explained by the hot photol uminescence effect.