Metastable zinc-blende MgS structure: Combined experimental and theoretical study

Abstract

MgS/ZnSe/GaAs multilayers with the MgS thickness ranging from 20 to 140 nm were grown at 300 °C by molecular beam epitaxy on [001] GaAs substrates. The samples were studied by using several X-ray methods and transmission electron microscopy. The coexistence of metastable zinc-blende (ZB) and rock-salt (RS) MgS structural phases were evidenced and discussed. The analysis of reciprocal space maps of the x-ray intensity distribution around asymmetrical reciprocal lattice nodes allowed us to determine the strain status of the MgS layers and to show that the ZB-MgS phase were pseudomorphic in also the case of the thickest film. The lattice parameter of the pure ΖΒ-MgS phase ranging between 0.56333< a MgS <0.56367 nm was obtained by extrapolation from X-ray diffraction data and

Growth and properties of wide bandgap (MgSe)n(ZnxCd1−xSe)m short-period superlattices

“…Relaxation of 26% was observed for the 1000 nm (sample 4) with a mismatch of 0.4%. This shows there is a significant increase in the critical thickness when compared to the Zn x Cd y -Mg 1–x–y Se random alloy of similar lattice mismatch, as also observed by others in (Si) n (SiGe) m SPSLs [6] This observation is of importance in magnesium containing II–VI alloys where strain induced transformation to rock salt limits the realization of good quality material and devices [14]. As the magnesium fraction increases, the strain tolerance of the SPSL decreases.…”

“…However, devices from these materials are limited at shorter wavelengths by the quality of a Zn x Cd y Mg 1–x–y Se component as we go to the wider bandgaps (2.9–3.2 eV), and bandgaps higher than 3.2 eV are not usually achieved in sufficiently good quality. At higher bandgaps (>2.9 eV) Zn x Cd y Mg 1–x–y Se growth becomes difficult due to rock-salt phase transformations of the metastable MgSe component [14]. We propose to replace the Zn x Cd y Mg 1–x–y Se barrier with short-period superlattices (SPSL) of Zn x Cd 1–x Se and MgSe to develop novel wide bandgap engineered materials.…”

Growth and stability of zinc blende MgS on GaAs, GaP, and InP substrates

“…The capping layers grown on top of the MgS clearly relax and modeling of the X-ray data from the thickest ZB MgS layers indicates these also relax. This was previously observed with layers grown on GaAs substrates 6,8 and is now confirmed for GaP and InP. In all cases, the dislocation densities are anisotropic and presumably incomplete, at least along [110].…”

“…In all cases, the dislocation densities are anisotropic and presumably incomplete, at least along [110]. It also suggests that despite MgS having very different elastic constants to the surrounding layers, 2,8,15 the mismatch dislocations are probably the same type.…”

Metastable II–VI sulphides: Growth, characterization and stability

“…The position of the MgS diffraction peak indicates that the layer is not completely relaxed. Subsequently, this layer, and several others grown under similar conditions were examined by high resolution X-ray diffraction and plan view TEM [40,41]. They showed very little relaxation and there was clear evidence of RS inclusions bounded by {1 1 1} planes and situated at stacking faults arising from the GaAs/ZnSe interface.…”