Structural properties and spatial ordering in multilayered ZnMgTe/ZnSe type-II quantum dot structures

Abstract

We report the structural properties and spatial ordering of multilayer ZnMgTe quantum dots (QDs) embedded in ZnSe, where sub-monolayer quantities of Mg were introduced periodically during growth in order to reduce the valence band offset of ZnTe QDs. The periodicity, period dispersion, individual layer thickness, and the composition of the multilayer structures were determined by comparing the experimental high resolution x-ray diffraction (HRXRD) spectra to simulated ones for the allowed (004) and quasi-forbidden (002) reflections in combination with transmission electron microscopy (TEM) results. Secondary ion mass spectroscopy (SIMS) profiles confirmed the incorporation of Mg inside the QD layers, and the HRXRD analysis revealed that there is approximately 32% Mg in the ZnMgTe QDs. The presence of Mg contributes to higher scattering intensity of the HRXRD, leading to the observation of higher order superlattice peaks in both the (004) and (002) reflections. The distribution of scattered intensity in the reciprocal space map (RSM) shows that the diffuse scattered intensity is elongated along the q x axis, indicating a vertical correlation of the dots, which is found to be less defined for the sample with larger periodicity. The diffuse scattered intensity is also found to be weakly correlated along the q z direction indicating a weak lateral correlation of the dots. V

Radiative transitions in stacked type-II ZnMgTe quantum dots embedded in ZnSe

“…However, we found that the addition of Mg in the QD layers contributed to the higher x-ray scattering intensity of the SL peaks. 17 For ZnMgTe/ZnSe, we observed SL peaks up to fifth order compared to the ZnTe/ZnSe case, 4,25 where we could resolve SL peaks only up to second order.…”

“…The simulation result showed that the average thicknesses of the ZnMgTe layer containing QDs and ZnSe barrier are about 0.1 and 3.6 nm, respectively. 17 The simulation result also showed that while most of Te is confined inside the QD-containing layer, there is a small amount of Te ($1%) diffusion inside the barrier. It is also found that there is approximately 30% Mg within the ZnMgTe layer.…”

“…The experimental x-2h curves showed that a set of subsidiary satellite peaks up to fifth order arises from interference between each of the layers symmetrically around the SL(0) peak for both the (004) and (002) reflections for ZnMgTe/ZnSe multilayer structures. 17 To extract structural parameters of the multilayer structure, the x-2h curves were simulated by the commercially available BEDE RADS program after an estimation of the initial fitting parameters. 17,25 For simulation purposes, we replaced the QD array by an effective layer, whose scattering factor is an average of the scattering factors of the dots and the crystal matrix.…”

“…17 To extract structural parameters of the multilayer structure, the x-2h curves were simulated by the commercially available BEDE RADS program after an estimation of the initial fitting parameters. 17,25 For simulation purposes, we replaced the QD array by an effective layer, whose scattering factor is an average of the scattering factors of the dots and the crystal matrix. The simulation result showed that the average thicknesses of the ZnMgTe layer containing QDs and ZnSe barrier are about 0.1 and 3.6 nm, respectively.…”

Structural and optoelectronic properties of Mg substituted ZTe (Z=Zn, Cd and Hg)

“…Liu et al [15] grown Mg x Zn 1-x Te (0 ≤ x ≤ 0.67) by molecular beam epitaxy on the (100) GaAs substrates and measured their band gap values by photoluminescence at 12 K, and by optical reflectivity at room temperature. Manna et al [16,17] reported the structural properties and spatial ordering of multilayer ZnMgTe quantum dots (QDs) embedded in ZnSe. Elakkad et al [18] investigated photoluminescence and optical properties of Mg x Zn l-x Te in the composition range 0 < x < 0.48.…”