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Spectroscopic Ellipsometric Properties of Ga1-xFexAs Dilute MagneticSemiconductors
호선 이,H. T. Oh,H. Y. Cho,H. Munekata,R. Moriya,강태동,Y. J. Park 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.III
We report pseudodielectric function data $<\!\epsilon\!>$ = $<\!\epsilon_1\!>$ + $i<\!\epsilon_2\!>$ of Ga$_{1-x}$ Fe$_x$As semiconductors grown on $GaAs$ substrates. The data were obtained from 1.5 to 6 eV using spectroscopic ellipsometry. Critical point (CP) parameters were obtained by fitting model lineshapes to numerically calculated second energy derivatives of $<\!\epsilon\!>$. The bandgap energies of $E_1$, $E_1+\Delta_1$, $E_0$', and $E_2$ were determined. We observed an increase of the $E_1$ and $E_1 + \Delta_1$ gap energy similar to that of ZnFe$_x$Se$_{1-x}$. The linewidth of CPs increased with increasing Fe compositions. The band gap energy shifts were mainly attributed to the alloying effect because the strain effect on the band gap energies was negligible. We also discuss the band gap shift in terms of an sp-d hybridization model.
Characteristics of molecular beam epitaxy-grown GaFeAs
Y.J.Park,H.T.Oh,C.J.Park,H.Y.Cho,손윤,김은규,R.Moriya,H.Munekata 한국물리학회 2002 Current Applied Physics Vol.2 No.5
Diluted magnetic semiconductors GaFeAs were grown by molecular beam epitaxy and characterized. Ga1. xFexAs ternary alloyswere obtained at the growth temperatureTs ¼ 200 .C ranging fromx ¼ 0:005 to 0.03. The eects of thermal treatment on behaviorsof defects, aecting to the magnetic properties of GaFeAs layer were particularly elucidated. As-grown samples were annealed attemperatures varying from 400 to 600.C. From the measurement of double crystal X-ray diraction, we observed Fe-related peakwhich shifted to a higher diraction angle as the Fe content increased, indicating that the lattice constant decreases with increasingFe content. In contrast, above the annealing temperature 500.C, the lattice constant becomes smaller than that of GaAs. Using thedeep level transient spectroscopy, various defects in GaFeAs layer were observed and identied in conjunction with magneticproperties.. 2002 Elsevier Science B.V. All rights reserved.