Negative spin polarization observed by the Hanle effect in quantum wells grown on processed surfaces
✍ Scribed by C. Mejía-García; A. Winter; M. López-López; A. Gilinsky; H. Pascher
- Publisher
- Elsevier Science
- Year
- 2010
- Tongue
- English
- Weight
- 880 KB
- Volume
- 150
- Category
- Article
- ISSN
- 0038-1098
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✦ Synopsis
A series of quantum well (QW) structures of Al 0.3 Ga 0.7 As/GaAs were characterized by photoluminescence spectroscopy with circularly polarized excitation at 1.6 K. The samples were grown by molecular beam epitaxy on a 500 nm thick GaAs buffer layer and contained three QW structures with thicknesses of 7, 5, and 3 nm, respectively. Four samples were prepared with different processing of the GaAs buffer layer surface (i: continuous growth, ii: in situ etching the GaAs buffer with Cl 2 at 70 °C, iii: at 200 °C, respectively and iv: air-exposed buffer). The influence of buffer surface preparation on sample characteristics was analyzed. Using the Hanle effect the interband lifetime τ and the spin lifetime τ s of the electrons were determined. A negative spin polarization was observed if the photon energy of the exciting light exceeds the difference between the spin-orbit band and the conduction band. This inverse circular polarization could be related to the quality of the sample.