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Báo cáo hóa học: " Electrostatically Shielded Quantum Confined Stark Effect Inside Polar Nanostructures"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Research Electrostatically Shielded Quantum Confined Stark Effect Inside Polar Nanostructures | Nanoscale Res Lett 2009 4 993-1003 DOI 10.1007 S11671-009-9347-1 NANO EXPRESS Electrostatically Shielded Quantum Confined Stark Effect Inside Polar Nanostructures Spilios Riyopoulos Received 5 December 2008 Accepted 12 May 2009 Published online 30 May 2009 to the authors 2009 Abstract The effect of electrostatic shielding of the polarization fields in nanostructures at high carrier densities is studied. A simplified analytical model employing screened exponentially decaying polarization potentials localized at the edges of a QW is introduced for the ES-shielded quantum confined Stark effect QCSE . Wave function trapping within the Debye-length edge-potential causes blue shifting of energy levels and gradual elimination of the QCSE red-shifting with increasing carrier density. The increase in the e h wave function overlap and the decrease of the radiative emission time are however delayed until the edge-localization energy exceeds the peak-voltage of the charged layer. Then the wave function center shifts to the middle of the QW and behavior becomes similar to that of an unbiased square QW. Our theoretical estimates of the radiative emission time show a complete elimination of the QCSE at doping densities 1020 cm 3 in quantitative agreement with experimental measurements. Introduction The presence of a strong inherent polar electric field in GaN 1 causes the well-known quantum confined Stark effect 2-4 QCSE regarding carrier behavior inside a QW Fig. 1a . The separation of the center of charge between electron and hole wave functions caused by the polar E-field reduces mutual overlap and the related S. Riyopoulos El Science Applications International Corporation McLean VA 22102 USA e-mail spilios.riyopoulos@saic.com emission probability. The lowering of the confined energy levels relative to the unperturbed square QW causes red-shifting of the emitted radiation during electron-hole recombination. This effect has been the subject of extensive perturbative 5 as well .