Diethyldisulphide as sulphur precursor for the low temperature metalorganic vapour-phase epitaxy of ZnS: growth, morphology and cathodoluminescence results

We report on the atmospheric pressure metalorganic vapour-phase epitaxy (MO VPE) growth of ZnS using diethyldisulphide (Et2S2) as sulphur precursor in combination with electronic grade dimethylzinc: triethylammine (Me2Zn : Et3 N). Et2S2 is used here for the first time as a substitute of diethylsulphid e (Et2S) to achieve low temperature ZnS growth in pyrolytic MOVPE. It is de monstrated that Et2S2 lowers the temperatures of the process by almost 150 degrees C with respect to Et2S, leading to growth rates in excess of 0.5 mu m/h just above 400 degrees C, Scanning electron microscopy observations an d 10 K cathodoluminescence (CL) measurements performed on the as-grown samp les are also reported. CL spectra show both free-to-bound and intense self- activated band emissions peaked at 3.683 and 2.58 eV, respectively. These e missions are attributed to unintentional Na and halogen (most probably Cl) doping of ZnS epilayers, likely arising from both Et2S2 and Me2Zn : Et3N pr ecursors. Finally, monochromatic CL images of the samples demonstrate the i nterplay between point defects induced radiative emissions and non-radiativ e recombinations associated with the epilayer extended defects. (C) 1999 El sevier Science B.V. All rights reserved.