MOVPE growth of ZnS on (100)GaAs using dimethylzinc and ditertiarybutyl sulphide precursors

Epitaxial ZnS films have been grown on (1 0 0)-oriented GaAs substrates by atmospheric pressure metal-organic vapour phase epitaxy (MOVPE), using dime thylzinc (DMZn) and ditertiarybutyl sulphide (DTBS) precursors for obtainin g high quality layers. A detailed study of the growth kinetics has enabled us to determine the influence of the deposition temperature T-g and the pre cursor partial pressures on the growth rate, surface morphology and crystal line quality of the layers. For the precursor partial pressures used here, high growth rates reaching 3.5 mu m/h have been achieved. X-ray measurement s result in a diffraction linewidth as low as 200 arcsec for films obtained with a ZnSe buffer layer. These data are a clear indication of the good cr ystalline quality of the films, when it is considered that a value of 180 a rcsec is measured for the GaAs substrate. The double-crystal X-ray measurem ents give additional support to this conclusion, since the values of the FW HM are 74 and 25 arcsec for the above film and the substrate, respectively. Under optimised growth conditions, the photoluminescence spectra are domin ated by excitonic emissions, with a free exciton linewidth of 4.7 meV. The experimental data clearly show the good quality of the epitaxial layers obt ained with the DMZn/DTBS combination, used here for the first time to the b est of our knowledge. (C) 1999 Elsevier Science B.V. All rights reserved.