HOMOGENEITY OF ZNSSE ZNSE MULTIQUANTUM WELLS GROWN BY METALORGANIC VAPOR-PHASE EPITAXY/

The ZnSxSe1-x (0 less than or equal to x less than or equal to 1) laye rs and multiquantum well structures studied here were grown in an atmo spheric or in a low-pressure metalorganic vapour phase epitaxy (MOVPE) reactor, respectively. For industrial device production, an excellent homogeneity across the whole wafer is required, so both reactors are equipped with rotating susceptors for two-inch wafers. X-ray diffracti on measurements of optimized multiquantum well structures grown with d iethylsulphur (DES) in the atmospheric-pressure reactor show very good structural properties and high reproducibility of the layer sequence indicated by sharp satellite peaks and pendellosung fringes. Also the near-band-edge photoluminescence (PL) spectrum hints on the excellent layer quality by sharp PL peaks (FWHM = 2.6 meV). The homogeneity of a multiquantum well structure across a two-inch wafer was determined fr om the local dependence of the PL blue-shift across the wafer. At the edge of the sample grown with H2S the blue-shift increases, which can be explained by an increased sulphur content or a lower thickness owin g to a decreased growth rate. However, Raman measurements taken at sam ples grown with DES show that the sulphur content is very homogeneous laterally, whereas the variation is much larger in samples grown with H2S. Homogeneity tests for ZnSSe grown with DES under low pressure or atmospheric pressure show no significant difference. Nevertheless, wit h H2S as a sulphur source, the gas phase depletion was reduced at low pressure. With increased gas flow velocity, both the sulphur content a nd the growth rate homogeneity were improved.