PDS spectra of a ZnMgO buffer layer after annealing at and a ZnO layer for comparison. The shift of the absorption edge of the buffer layer with respect to the ZnO layer indicates intermixing of MgO and ZnO upon annealing. The RHEED image of the annealed buffer is depicted in the inset.
Absorption coefficient of the investigated samples at a temperature of 5 K. Excitonic features are clearly visible. The peak position of the near band edge luminescence is marked with squares.
Urbach energy and Stokes shift in the investigated ZnMgO films as a function of the Mg content .
Low-temperature (4.2 K) PL spectra of the different layers in logarithmic scale. Arrows show the phonon replica, the shift in the deep and band edge luminescence is denoted by dotted lines. The inset shows a magnification of the excitonic region of the ZnO sample.
(a) Evolution of the peak position of the deep and near band edge luminescence. Both emissions show a systematic blueshift. (b) FWHM of the band edge PL as a function of the Mg content. The solid line is a calculation of the FWHM according to the model suggested in Refs. 20 and 21.
Temperature dependence of the band edge luminescence of a -layer. The typical S-shape behavior of ternary alloys is evident. The energetic position of the emission maximum as a function of temperature is shown in the inset.
Arrhenius plots (semilogarithmic scale) of the normalized integrated PL intensity for the different alloys. The straight lines represent the slopes used for the determination of the activation energies. The activation energy and the Stokes shift is plotted as a function of the Mg content in the inset [the open circles are taken from Ref. 13].
scans of films with M-contents and 0.37. The Pendellösungen of the 002 reflex, shown in the inset, was used to determine the layer thickness. Reflexes marked with “×” can be assigned to the sample holder.
FWHM of 002 and 101 rocking curves of layers measured by HRXRD. The width of the symmetric rocking curve is almost independent of the Mg content, whereas the asymmetric reflex broadens with increasing Mg content.
Out-of-plane and in-plane lattice parameters of layers extracted from reciprocal space maps around the 205 reflex. The -lattice parameter decreases with increasing Mg content, whereas the -lattice parameter remains constant, indicating pseudomorphic growth on the ZnMgO-buffer layer.
Mg beam equivalent pressure during growth, Mg concentration, layer thickness, peak energy of the PL maximum at 5 K, and concentration of free electrons of the investigated ZnMgO layers.
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