The photoassisted MOVPE growth of ZnSSe using tertiary-butylmercaptan

We have conducted a study of the compositional control of epitaxial ZnSySe1 -y grown by photoassisted metal organic vapor phase epitaxy (MOVPE) (250 to rr, 340 degrees C, UV = 14 mW/cm(2)) on GaAs (100) substrates. We have achi eved lattice matched ZnSSe films on GaAs substrates using photoassisted gro wth using dimethylzinc (DMZn), dimethylselenide (DMSe), and tertiary-butylm ercaptan (t-BuSH) as precursors. In addition, we have obtained sulfur compo sitions (y), ranging from 0.023 to unity (ZnS). The growth rate of the ZnS was 1 mu m/h, which was previously unattainable by our group using diethyls ulfur. The closely lattice matched sample (y = 0.07 as determined by high r esolution x-ray diffraction) showed a near band edge peak intensity (NBE) t o deep level emission intensity (DLE) ratio of 77 to 1, as determined by ro om temperature photoluminescence measurements. We have examined the sulfur incorporation as a function of source mole fractions, UV intensity, and gro wth temperature and found that optimized growth conditions (optimized for r ange of compositions possible, and NBE/DLE ratio) are X-DMZn = 1.5 X 10(-4) , X-DMSe = 3 x 10(-4), UV = 14 mW/cm(2), growth temperature = 340 degrees C . X-DMZn and X-DMSe are the mole fractions of DMZn and DMSe, respectively. We have found the growth rate to be 1 mu m/h for y = 0.023 to 0.24 for thes e optimized conditions. It was found that to achieve sulfur compositions of less than 0.9, the t-BuSH mole fractions had to be kept low. Higher UV int ensities increased the incorporation of selenium, while also lowering the m aterial quality (NBE/DLE ratios). We have shown that the optical material q ualities of ZnSSe films grown with t-BuSH are much better than ZnSSe films grown with DES.