EFFECT OF MOVPE GROWTH-PARAMETERS ON THE PHOTOLUMINESCENCE LINEWIDTH OF ZNSXSE1-X (0-LESS-THAN-OR-EQUAL-TO X LESS-THAN-OR-EQUAL-TO-1) EPILAYERS ON GAAS

In this work we report the effect of growth parameters on the properties of ZnSxSe1-x (0 less-than-or-equal-to x less-than-or-equal-to 1) grown by atmospheric pressure MOVPE. To study the effect of sulphur precursors on the layer quality we use DES or H2S together with DESe and DEZn as starting materials. The DES is used to grow mirror like ZnSxSe1-x (x less-than-or-equal-to 0.1), whereas higher sulphur contents and mirror-like surfaces were achieved only with H2S. However, premature reactions between the metalorganic compounds and the H2S occur X-ray diffraction measurements and temperature resolved pbotoluminescence (PL) measurements are used to judge the layer quality. The PL spectra of ZnSxSe1-x (x less-than-or-equal 0.1) show sharp excitonic structures; e.g., the FWHM of the I(x) emission attributed to a donor bound exciton is 1.7 meV in ZnS0.04Se0.96. In ZnSxSe1-x (x > 0.2) the near band edge emission broadens due to alloy fluctuations and increased lattice mismatch. Therefore we obtain a FWHM of only 44 meV at 10 K from ZnS0.65Se0.35 layers.