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    Öğe
    Determination of electronic band structure of quaternary ferromagnetic Ga0.97-yMn0.03CryAs epitaxial layers
    (Elsevier, 2023) Donmez, Omer; Gunes, Mustafa; Henini, Mohamed; Erol, Ayse
    Introducing transition metals to conventional III-V semiconductors anomalously changes their fundamental characteristics, such as electronic, magnetic, and structural properties. In this study, we show that the valence band anti-crossing (VBAC) model can be exploited to calculate the electronic band structure of the quaternary Ga0.97-xMn0.03CrxAs epitaxial layers. In this model, the localized Mn and Cr defect states interact with the valence band states (VB), reconstructing VBs and splitting each VB state. The splitting top of the VB state forms an impurity band (IB) and fundamental VB edge. Photomodulated reflectance (PR) spectroscopy is exploited to determine optical transition energies at room temperature. PR spectra were analyzed with the third derivative functional form (TDFF) signal's line shape. The experimental optical transition energies, including band-to-band and spin split-off band transitions, match the calculated optical transition energies by the VBAC model. In the calculation, the interaction energy between localized Mn/Cr-energy level and valence band edges is experi-mentally determined as 0.7 eV.
  • [ X ]
    Öğe
    Structural and optical properties of diluted magnetic Ga1-xMnxAs-AlAs quantum wells grown on high-index GaAs planes
    (Indian Acad Sciences, 2017) Gunes, Mustafa; Gumus, Cebrail; Gobato, Yara Galvao; Henini, Mohamed
    We report on the structural and optical properties of Ga1-xMnxAs-AlAs quantum wells (QWs) with x = 0.1% grown by molecular beam epitaxy (MBE) on semi-insulating GaAs substrates with orientations (100), (110), (311)B and (411)B. Atomic force microscopy (AFM), X-ray diffraction (XRD) and photoluminescence (PL) techniques were used to investigate these QWs. AFM results have evidenced the formation of Mn-induced islands, which are randomly distributed on the surface. These islands tend to segregate for samples grown on (110) and (411)B planes, while no clear segregation was observed for samples grown on (100) and (311)B orientations. Results show that the PL line width increases with Mn segregation. XRD measurements were used to determine 2 theta, d and cell parameters.