Optical properties of ZnSxSe1-x (x < 0.18) random and ordered alloys grownby metalorganic atomic layer epitaxy

ZnSxSe1-x (x < 0.18) random alloy and ordered alloy were grown on GaAs (0 0 1) substrate by metalorganic chemical vapor deposition in ALE mode (MOCVD- ALE) using dimethylzinc, H2Se and H2S as source materials. In order to inve stigate the strain effect of ZnSxSe1-x. epilayers, heavy hole (hhx) and lig ht hole (lhx) exciton peaks in PL spectra were monitored as a function of S composition. The identification of hhx and lhx peaks was confirmed by phot oreflectance spectroscopy. The S composition at which lattice matching took place was determined to be 5.6%. The full-width at half-maximum (FWHM) of hhx peak increased and deep-level emission appeared in the PL spcctra as th e S composition increased. For the ordered alloy, the FWHM of exciton peak was narrower than that for the random alloy and the deep level emission was suppressed. An analysis of broadening of the exciton line show that the op tical properties of random alloy are influenced by alloy potential and that the alloy potential fluctuation is significantly constrained in the ordere d alloy. (C) 2000 Elsevier Science B.V. All rights reserved.