Highly confined excitons in MgS/ZnSe quantum wells grown by molecular beam epitaxy

Abstract

MgS has been grown by molecular beam epitaxy in the zincblende crystal structure on GaAs (100) 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 $0.5619\ifmmode\pm\else\textpm\fi{}0.0001\mathrm{nm}$ 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 ${E}^{X}(1s--2s)>h{\ensuremath{\nu}}_{\mathrm{LO}}$ 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.