MgS has been grown by molecular beam epitaxy in the zincblende crystal structure on GaAs ͑100͒ substrates using a technique where the sources are Mg and ZnS. Layers up to 134 nm thick have been grown without any degradation in the crystal structure. The lattice constant was found to be 0.5619Ϯ0.0001 nm and Poisson's ratio was estimated to be 0.425. The success of this growth technique has allowed the fabrication of MgS/ZnSe/MgS quantum wells that show sharp photoluminescence and transmission spectra indicating less than 1 ML fluctuations of the well widths. The small inhomogeneous broadening of the samples has allowed magneto-optical studies of the exciton absorption where the observation of higher excited exciton states have been observed and the exciton binding energies, E X , have been measured directly, notably E X (1s -2s) Ͼh LO in a 5 nm well. The full width at half maximum of the heavy-hole absorption transitions for this sample has been measured as a function of temperature and no broadening of the excitonic transitions has been observed up to 150 K showing that the exciton-LO phonon scattering has been suppressed.
Zinc blende MgS has been grown on GaAs by molecular beam epitaxy using a novel method where the sources were Mg and ZnS. A reaction at the surface results in the formation of MgS layers with a Zn content estimated by secondary ion mass spectrometry and Auger spectroscopy to be between 0.5% and 2%. Double crystal x-ray rocking curve measurements of ZnSe/MgS/ZnSe layers show layers with good crystallinity. Using this growth technique layers up to 67 nm thick have been grown. Photoluminescence measurements of MgS/ZnSe/MgS single-quantum-well structures show that the confinement of the heavy hole excitons can be as large as 430 meV for a 1.7 nm well.
Epitaxial liftoff is a post-growth process by which the active part of a semiconductor heterostructure, the epitaxial layer, is removed from its original substrate and deposited onto a new substrate. This is a well established technique in GaAs-based heterostructures where epitaxial liftoff can be achieved by exploiting the contrast in the etch rates of GaAs and AlAs in hydrofluoric acid. We report here successful epitaxial liftoff of a ZnSe-based heterostructure. We find that a metastable layer of MgS acts as a perfect release layer based on the huge contrast in the etch rates of ZnSe and MgS in hydrochloric acid. Epitaxial liftoff of millimeter-sized ZnSe samples takes a fraction of the time required for GaAs liftoff. Photoluminescence experiments confirm that the liftoff layer has the same optical characteristics as the original wafer material.
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