Search

Abstract: A series of hot (600 °C) and room temperature C+/Al+ co-implanted 6H–SiC epitaxial films, under different implantation dose levels and high temperature (1550 °C) post-annealing, were studied by a variety of structural and optical characterization techniques, including secondary ion mass spectroscopy, high resolution X-ray diffraction, Fourier transform infrared reflectance, micro-Raman and photoluminescence (PL) spectroscopy. The damage and amorphization of SiC layer by co-implantation, and the elimination/suppression of the implantation induced amorphous layer via high temperature annealing are observed. The recovery of the crystallinity and the activation of the implant acceptors are confirmed. The results from hot or RT co-implantation are compared. [Copyright &y& Elsevier]

Abstract: Two sets of (Al x Ga1−x )0.5In0.5P films were grown on lattice-matched GaAs by low pressure metalorganic chemical vapor deposition under different conditions and studied by Nomarski microscopy (NM), atomic force microscopy (AFM), photoluminescence (PL) and Raman scattering. NM and AFM images show cross-hatch patterns, related to dislocations and lattice mismatch, from one set of samples, but none from another set of films. Comparative PL and Raman measurements and analyses indicated the correlation between surface and optical properties. The degree of variations in compositions and film quality with the growth conditions was found from the spectral analyses. Raman spectral features are more sensitive to the sample growth parameter variations. The line shape analysis of line width, integrated intensity ratio and spatial correlation model fitting leads to information about the order of the sample crystalline quality. The optimum growth conditions have been obtained from our comprehensive analyses. [Copyright &y& Elsevier]

Abstract: The wavelength shifts in the photoluminescence (PL) from low indium composition (∼ 3%) InGaN epitaxial thin films, grown on sapphire substrates by metalorganic chemical vapour deposition, has been studied by a combination of experiment and theory. As temperature increases from 6 K, the PL peak energy red-shifts very slightly first, then blue-shifts to reach a maximum at near 100 K, and red-shifts again till room temperature. This unique PL behaviour, indicating the existence of the phase separation, is interpreted qualitatively from the spatial variation of band structure due to the In-compositional fluctuation. Theoretical calculation, based upon a model involving the band-tail states in the radiative recombination, explains the experimental data successfully. [Copyright &y& Elsevier]

Abstract: Si1−x Ge x layers sandwiched between Si were grown at low temperature of 450 °C by molecular beam epitaxy. A comprehensive characterization has been performed on these heterostructures by multiple techniques, including X-ray diffraction (XRD), photoluminescence, Raman scattering, Fourier transform infrared (FTIR) spectroscopy, Rutherford backscattering spectrometry (RBS), ion channeling and secondary ion mass spectroscopy (SIMS). XRD confirmed the single crystallinity and the (100) orientation of the Si1−x Ge x layer. The Ge compositions and layer thicknesses were precisely determined by RBS. FTIR measurements revealed the vibration modes of Si–O–Si from the oxidation on surface and Si–H due to the hydrogenization during growth. [Copyright &y& Elsevier]

Abstract: InGaAsP/InP multiple quantum wells with quantum well intermixing (QWI) have been prepared by Impurity-Free Vacancy Disordering (IFVD). The luminescent characteristics were investigated using photoluminescence (PL) and photoreflectance (PR), from which the band gap blueshift was observed. Si3N4, SiO2 and SOG (spin on glass) were used for the dielectric layer to enhance intermixing from the out-diffusion of Group III atoms. All samples were annealed by rapid thermal annealing (RTA). The results indicate that the band gap blueshift varies with the dielectric layers and the annealing temperature. The SiO2 capping was successfully used with an InGaAs cladding layer to cause larger band tuning effect in the InGaAs/InP MQWs than the Si3N4 capping with an InGaAs cladding layer. On the other hand, samples with the Si3N4–InP cap layer combination also show larger energy shifts than that with SiO2–InP cap layer combination. [Copyright &y& Elsevier]

Highly textured lead lanthanum titanate (Pb1-xLax)TiO3 (PLT) thin films have been grown on fused quartz substrates by metalorganic chemical deposition (MOCVD). A series of PLT with different x between 0 and 0.32 were prepared and studied by Raman scattering. Raman spectra, measured at 300 K and 80 K, showed the features from the PLT film and quartz substrate. By using a “difference Raman” technique, more PLT modes are shown. The variations of the PLT Raman modes with the La composition and the measurement temperature are studied, and related physical phenomena and problems are discussed. [Copyright &y& Elsevier]

Examines the Raman scattering and x-ray diffraction of lead lanthanum titanate thin films. Use of metalorganic chemical vapor deposition to prepare the thin films; Alignment of crystallographic axes of the films; Decrease in the tetragonality of the crystal structure.

Examines the Raman spectra of lead titanate thin films grown by metalorganic chemical vapor deposition. Use of single-crystal KTaO[sub 3] and fused quartz as substrates; Overview of soft-mode theory; Shift in optical mode frequencies for the thin films and substrates.

Abstract: A series of GaN thin films were grown on Si substrate under different conditions using metalorganic chemical vapor deposition (MOCVD) and characterized by Nomarski microscopy (NM), optical reflectance (OR), high-resolution X-ray diffraction (HRXRD), Raman scattering (RS) and photoluminescence (PL). NM showed different patterns for GaN/Si grown under different growth and source flow parameters. XRD, RS and PL measurements confirmed their wurtzite crystalline GaN structures, and the corresponding line shape analyses revealed their difference corresponding to the NM observations. The control and improvement of the crystalline cracking in GaN/Si are discussed. [Copyright &y& Elsevier]

Abstract: Wurtzite-structure MgxZn1−xO materials with five different compositions of x from 0 to 0.14 were grown on sapphire substrates by metalorganic chemical vapor deposition. It was found that increasing Mg content in the MgxZn1−xO not only increased the band gap energy of the film but was also beneficial to the epitaxial growth of p-type MgxZn1−xO without using any doping sources. In addition, the combined ultraviolet photoluminescence (PL) and Raman scattering spectra were measured with PL–Raman signals obtained together, showing a blue-shift of PL band and variation of resonant Raman multi-order longitudinal optical phonon modes with an increase of Mg content. [ABSTRACT FROM AUTHOR]

Abstract: We report the successful growth of thin GaN layers on (111) orientated Si substrates utilizing a newly developed pulse source injection molecular beam epitaxial (PSIMBE) technique. RHEED patterns showed that two-dimensional layer-by-layer growth started at a very early stage during deposition (within 20 nm). AFM studies showed that an almost atomically smooth surface was obtained with an area RMS roughness of less than 0.2 nm. The crystal structure and quality were determined from high resolution 2-Theta-Omega scan and exhibited only three strong and sharp lines at 28.56°, 34.70° and 73.05° due to the Si substrate and the single crystalline wurtzite (w-) GaN (0002) and (0004), respectively. Raman scattering study showed the characteristic w-GaN E2 band at 565 wave-numbers and the longitudinal optical (LO) phonon-plasma coupling mode at 731 cm− 1. These data indicate the success of MBE growth of single crystalline w-GaN thin layers on the order of less than 100-nm thick on Si substrates without using a complicated buffer structure. [Copyright &y& Elsevier]