Showing papers by "David W Parent published in 2000"
TL;DR: For ternary heteroepitaxial layers, the independent determination of the composition and state of strain requires x-ray rocking curve measurements for at least two different hkl reflections as discussed by the authors.
Abstract: For ternary heteroepitaxial layers, the independent determination of the composition and state of strain requires x-ray rocking curve measurements for at least two different hkl reflections because the relaxed lattice constant is a function of the composition. The usual approach involves the use of one symmetric reflection and one asymmetric reflection. Two rocking curves are measured at opposing azimuths for each hkl reflection. Thus, it is possible to account for tilting of the hkl planes in the epitaxial layer with respect to the hkl planes in the substrate, by averaging the peak separations obtained at the opposing azimuths. This procedure presents a practical problem in the case of asymmetric reflections, for which the tilting can only be canceled if the rocking curve for one azimuth is obtained using θ−φ incidence. A preferable approach, which provides sharper, more intense rocking curves and greater experimental accuracy, is to measure both asymmetric rocking curves at θ+φ incidence. This approach ...
16 citations
TL;DR: In this paper, the authors achieved lattice matched ZnSSe films on GaAs substrates using photo assisted growth using dimethylzinc (DMZn), dimethylselenide (DMSe), and tertiary-butylmercaptan (t-BuSH) as precursors.
Abstract: We have conducted a study of the compositional control of epitaxial ZnSySe1-y grown by photoassisted metal organic vapor phase epitaxy (MOVPE) (250 torr, 340°C, UV=14 mW/cm2) on GaAs (100) substrates. We have achieved lattice matched ZnSSe films on GaAs substrates using photoassisted growth using dimethylzinc (DMZn), dimethylselenide (DMSe), and tertiary-butylmercaptan (t-BuSH) as precursors. In addition, we have obtained sulfur compositions (y), ranging from 0.023 to unity (ZnS). The growth rate of the ZnS was 1 µm/h, which was previously unattainable by our group using diethylsulfur. The closely lattice matched sample (y=0.07 as determined by high resolution x-ray diffraction) showed a near band edge peak intensity (NBE) to deep level emission intensity (DLE) ratio of 77 to 1, as determined by room temperature photoluminescence measurements. We have examined the sulfur incorporation as a function of source mole fractions, UV intensity, and growth temperature and found that optimized growth conditions (optimized for range of compositions possible, and NBE/DLE ratio) are XDMZn=1.5 × 10−4, XDMSe=3×10−4, UV=14 mW/cm2, growth temperature=340°C. XDMZn and XDMSe are the mole fractions of DMZn and DMSe, respectively. We have found the growth rate to be 1 µm/h for y=0.023 to 0.24 for these 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 intensities increased the incorporation of selenium, while also lowering the material quality (NBE/DLE ratios). We have shown that the optical material qualities of ZnSSe films grown with t-BuSH are much better than ZnSSe films grown with DES.
3 citations