S elective X-ray absorption spectroscopy of self-assembled atom in InAs quantum dot

To discuss the local structure of an atom in the self-organized InAs quantum dot (QD), we perform a site-selective X-ray absorption fine structure (XAFS) measurement, employing the capacitance XAFS method. Since the X-ray-induced photoemission of confined electrons in a QD via inner-shell absorption can be detected by capacitor, the photon energy dependence of the capacitance provides the XAFS spectrum of the atom in the QD. It is found that when the bias voltage applied to the capacitor aligned the Fermi energy with the quantum level, the site-selectivity is enhanced. The peak energy shift of | 1.5 eV is observed in the site-selective XAFS spectrum of an As atom in QD. The molecular orbital calculation indicates that the energy shift originates from the point defect at the boundary between an InAs QD and a GaAs barrier layer.  2003 Elsevier Science B.V. All rights reserved.