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Research was conducted to examine the carrier recombination and scattering dynamics in self-organized InAs/GaAs quantum dots using continuous wave and time resolved photoluminescence spectroscopy and time decay photoluminescence calculations. A Monte Carlo model was developed for data analysis. Results show that the model is critical in determining the relative contributions of the different recombination and scattering mechanisms.

Research was conducted to examine the electrical conductivity of semiconducting magnesium vanadate glasses for a wide composition range in the temperature ranging from 80 K to 500 K. Findings were analyzed in the framework of various hopping models. The parameters derived from the fits of the experimental data to the multiphonon assisted hopping model appear reasonable and are in agreement with the glass composition.

Research was conducted to examine the effect of thermal processes on the optical properties, namely, the refractive index, optical gap, Tau coefficient and Urbach energy, of SiN(sub x):H films. Chemical vapor deposition method assisted by an electron cyclotron resonance generated plasma was used to deposit the films with three different nitrogen to silicon ratios. Results demonstrate that the thermal stability of the films depends on starting compositions above and below the percolation threshold for the Si-Si bonds.

Research was conducted to examine the pseudodielectric-function spectra of amorphous selenium (a-Se) in the 1.2-5.2 eV photon-energy ranged calculated by spectroscopic ellipsometry at room temperature. The measured spectroscopic ellipsometry data were analyzed based o the Jellison-Modine model. An analysis of the dielectric-related data, such as the complex refractive index, absorption coefficient and normal-incidence reflectivity, of a-Se was also performed.

Research was conducted to systematically examine the deep photoluminescence bands in CuGaSe2 and CuInS2 single crystals. The band was shown to have a similar doublet structure with the two D1D2 subbands separated by about 100meV in both of the as-grown materials. Results show that the defects constituting the D1 and D2 band recombination centers are chemically identical but structurally slightly different.

Research was conducted to examine the fundamental optical properties of AgGaTe2, a nonlinear optical (NLO) semiconductor. The objective was to provide the necessary data to accurately evaluate its potential as a NLO crystal. The properties include the range of transparency, the temperature dependence of the band gap, the electrical transport properties and the natiev defect related subband gap photoluminescence. The measured properties were used to assess the potential of AgGaTe2 for the wavelength conversion processes of second-harmonic match at room temperature.

The optical properties of Si-Ge semiconductor nano-onions have been studied. Nano-onions are core shell nanocrystals with semiconductor cores surrounded by a shell of different and epitaxially matched semiconductors. In the Si-Ge semiconductor, epitaxial matching produces a Si layer around Ge core resulting in a quantum well made of Ge. The electron hole pair is confined within the quantum well leading to better luminescence. Maintaining the Ge and Si lattice constants will produce the biggest band gap.

Research was conducted to examine the pseudomorphic Ga(sub 1-x)In(sub x)N/GaN single heterostructures in the composition range 0

Research was conducted to quantitatively examine the nonlinear behavior of variations in the measured transmittance in the GaSe when samples are optically excited. The transmission pulses derived at various temperatures and incident intensities were described. A semiphenomenological model is then used in the measurement of the absorption coefficient that permits the reproduction of the transmission time response.

Research was conducted to examine the use of postgrowth chemical reduction to controllably increase the electrical conductivity and the optical absorption of single-crystal lithium niobate. The objective was to devise and analyze a method for generating a modified material free from electrical charging and photolith back-reflection problems. Observed optical absorptivity and dc electrical conductivity increases are expected to yield benefits for surface acoustic wave device fabrication processing.

The optical constants of GaP, InP and InAs in the spectral range from 1 to 6 eV were modeled. An extension of the Adachi model with the adjustable broadening function was employed. Adjustable broadening was modeled by supplanting the damping constant with the frequency-dependent expression. The enhanced flexibility of the model allowed excellent agreement with experimental data. The relative rms errors for the refractive index were 1.2% for GaP, 1.0% for InP and 1.6% for InAs.

Surface states in nanostructured TiO(sub 2) electrodes have been investigated using spectroelectrochemical techniques. Results show that a small optical response caused by trapped electrons takes place at applied potentials positive of V(sub fb), a response which differs significantly from that of conduction band electrons. The extinction coefficient of an electron trapped in a surface state is more than three times higher than that of a conduction band electron at the same wavelength. The location and density of the surface states were also identified.

The spectral performances of nonideal rectangular Bragg gratings, integrated in a rib waveguide, are analyzed by a multilayer approach based on the effective-index method. The effects of errors on the photolithographic definition of the grating, that is, period and shape, and of errors on the control of etching depth are investigated. Also the influence of the stitching error, which is unavoidable when the grating is realized by means of electron-beam photolithography, is addressed. A novel analytical approach that extends coupled-mode theory to the analysis of real gratings is also presented.

Research was conducted to examine the optical characteristics and patterning of patternable inorganic-organic hybrid films synthesized from diethoxydimethylsilane and Ti(OC2H5)4 modified with ethyl acetoacetate. Fourier-transform infrared study demonstrated that the irradiation of UV light at 254 nanometers led to the decomposition of the chelate complex of Ti(OC2H5)4 and EAcAc in the hybrid films. Results indicate that the solubility change by UV irradiation makes the fabrication of patterned hybrid films a possibility.

Research was conducted to examine the photorefractive and optical characteristics of Nb-doped BaTiO3. The gradual modification of the photorefractive properties of BaTiO3 was carried out through the addition of Nb which changed the charge carrier from hole to electron. The deep and shallow trap model with hole as the principal carrier explains two beam coupling gain along with electron-hole competition. The dark conductivity increased very fast and the electron became the major carrier after the compensation point, when an absorption at about 600 nanometers evolved.

The optical properties of Si-SiO2 interfaces are studied using variable-angle spectroscopic ellipsometry (VASE), with emphasis on the phase difference, Delta and amplitude ratio, tan psi for the s and p waves. Two models of the oxide layer in Si were derived to determine the interface sensitivities of cos Delta and tan psi to the VASE data. Results show that the sensitivities for cos Delta and tan psi have maximum values at the same angle of incidence and photon energy in the s-wave antireflection condition.

The spectral dependence of the complex dielectric function, epsilon(E) = epsilon1(E)+iepsilon2(E) of chalcopyrite semiconductors CuGaSe2 and CuInSe2 is studied using spectroscopic ellipsometry. Epsilon(E) spectra show distinct structures at the lowest direct gap and higher energy critical points. Dielectric-function-related constants such as complex refractive index and absorption coefficient are also discussed.

The primary mechanisms of electron-hole generation in a semiconductor caused by the adsorption of a sub-band gap photon have been studied. Electron-hole generation involves optical and thermal transitions between delocalized valence or conduction band states and localized band gap states. Free carrier generation may result in sub-band gap photocurrent flow in insulators and in n- and p-type semiconductors if there is a retrieval layer in which electrons and holes are effectively separated.

ZnS nanoparticles produced by chemical precipitation of Zn2+ with sulfur ions in aqueous solution were subjected to ultraviolet radiation. This revealed the detailed structure in the luminescence spectra. A doublet pattern found in the long wavelength region is due to the coexistence of the two crystalline forms in ZnS particles. The visible luminescent radiation at 590.1 nm is caused by Mn impurities. The dominant emission band at short wavelengths indicated a quadruple fine structure.

The properties of N-type 3C-SiC layers grown on p-type (001) Si substrates were studied through the usual photoconductivity decay technique. A N2 laser was the excitation source. A very slow component with a time constant bigger than 1 ms was seen in the photoconductivity decay curves. A numerical simulation using a trap with very small capture cross section for electrons was successful in representing the main qualitative characteristics of the experimental findings.

Research was conducted to evaluate the direct and inverse interface composition profile of InAlAs-InP heterostructures grown via gas source molecular beam epitaxy. A new transition scheme was developed using results from the injection-dependent energy, lifetime and polarization. This involves spatially indirect radiative combinations which have lower injection limits and longer lifetime.

Research was conducted to examine the interface between Ga0.5In0.5P and GaAs using angle resolved x-ray photoemission spectroscopy. Both compounds were grown using gas source molecular beam epitaxy. Results showed that indium segregation is effective at 500 degrees centigrade. The growth of two layers of anions in rapid succession results in the incorporation of excess arsenic in the GaInP epilayers and diffuse interface.

The photoluminescence of Ga0.54In0.46As0.12P0.88 layers grown by metalorganic vapor phase epitaxy on differently oriented GaAs substrates was studied. Room temperature photoluminescence polarization spectroscopy revealed valence-band splitting due to symmetry breaking in ordered quaternary alloys. Single- and two-variant ordering was recognized by high resolution x-ray diffraction on samples grown on (001) GaAs substrates misoriented 2 deg off to {111} B and on just oriented ones, respectively.

Comprehensive reflectivity investigations were performed on hexagonal GaN films grown by molecular beam epitaxy on GaAs substrates in the energy range of 1.4 to 3.8 eV at room temperature. Findings indicate that the reflectivity is strongly affected by a surface roughness. Also, the optical data indicate the development of an interface layer between the film and the substrate which is in agreement with findings from transmission electron microscopy studies.

The optical characteristics of the chromium doped spinel type semiconductor alpha-ZnAl2S4 were investigated over the temperature range of 2-540 deg K. The intrinsic photoluminescence revealed an intense ultraviolet peak at 381 nm at 296 deg K. A strong crystal field in the octahedral sites of the alpha-ZnAl2S4 host lattice occupied by Cr3+ impurities was observed. The emission caused by a Cr4+ center contributed to the infrared luminescence and had population inversion up to at least 378 deg K around 850 nm.

Research was conducted to examine numerically the propagation of strong picosecond optical pulses in semiconductor optical amplifiers by considering carrier heating, two-photon absorption, ultrafast nonlinear refraction and spectral hole-burning. Results are in good agreement with the published experimental measurements in both the time and frequency domains for strong input pulses. Results reveal that the effects of two-photon absorption and ultrafast nonlinear refraction are very important in determining the output pulse properties for pulse energy larger than 1 pJ.

Research was conducted to investigate some of the zero-dimensional physics controlling the performance of devices that could be made from self-assembled InAs-GaAs quantum dots. The strain distribution as well as the electronic spectra were studied via the valence force-field model and an eight-band k.p model, respectively. Results indicate that the effective mass approach for the conduction band provides significant errors and also suffers from the problem that there is no nonarbitrary choice for the effective mass.

The group index of Cd0.88Zn0.12Te was determined by time-of-flight mass spectroscopy near the exciton energy at 10 K, in the energy range between 1.61 and 1.65 eV. The standard model which depends on a single excitonic contribution to the dielectric constant results into erroneous optical constants for CdZnTe. On the other hand, experimental results are in good agreement with a model which considers all excitonic states.

Research was conducted to examine the growth kinetics and optical properties of self-organized GaN quantum dots. They were fabricated by controlling the Stranski-Krastanov growth mode of GaN deposited by molecular beam epitaxy on AlN. Observations include evidence for the ripening of dots under vacuum which results in changes in dot size distribution. Results also indicate the strongly zero-dimensional character of the nanostructures.

A comprehensive model for the calculation of the room-temperature polarization-dependent absorption coefficients and refractive index was developed. Results demonstrate that Group-III-only interdiffusion yields compressive strain and leads to a band-edge red shift and refractive index enlargement while the tensile strain induced by Group-V-only interdiffusion leads to a vice versa effect. The calculated results were in good agreement with available measured data.

Research was conducted to investigate the lateral and cross-well transport of highly and moderately excited carriers in Si(sub 0.83)Ge(sub 0.17)/Si superlattices. To calculate the reciprocal contribution of carrier laterial and cross well diffusion into the relaxation process, the pump-and-probe techniques of picosecond transient reflectometry and dynamic gratings were used in the study. Results demonstrate that the combination of these methods provide the means to separate and quantify the mutual contribution from the parallel and perpendicular transport of carriers.

The first inclusion of GaAs in the pores of MCM-41 is reported. Of special concern is the optical characterization of a direct-gap semiconductor heterostructure synthesized by deposition of GaAs into the channels of MCM-41 using metalloorganic chemical vapor deposition. The GaAs/MCM-41 heterostructures exhibit blue-shifted absorption and broad visible photoluminescence even at room temperature. The MCM-41 pore diameter determines the photoluminescence, thus supporting formation of size-quantized semiconductor crystallites whose growth is restricted by the diameter of the pores of MCM-41.

Variable angle of incidence spectroscopic ellipsometry between 0.75 eV and 6.5 eV was conducted to examine the optical constant spectra of silicon and thermally grown silicon dioxide. The optical constants for thermal silicon dioxide were found to be about 0.4% higher in index than bulk glasseous SiO2 values. Results also show that the silicon optical constants are in agreement with previous ellipsometric, long wavelength prism and near band gap transmission measurements.

Research was conducted to examine the temperature dependence of erbium 4f-shell luminescence decay time and intensity in silicon based on a multiphonon-assisted energy transfer model. The energy mismatch was calculated for the Er4f-shell excitation process and the energy back-transfer process while the energy positions of the trap levels were computed from estimated values. Results suggested a strong reaction between the Si host and the Er4f shell in the former.

Er3+ and Yb3+ co-doped fluoroindate glasses were examined using optical absorption, Stokes and anti-Stokes photoluminescence. Upconversion processes were observed as a function of photon excitation energy and temperature for compounds that were prepared with a fixed 2 mol % ErF3 concentration and YbF3 contents ranging from 0 to 8 mol %. Two mechanisms for the anti-Stoke photoluminescence were identified and analyzed based on the experimental data.

Research was conducted to examine the optical properties (Al(sub x)Ga(sub 1-x))0.52In0.48P at the crossover from a direct-gap to an indirect-gap semiconductor. Three epitaxial layers deposited by solid-source molecular beam epitaxy with varying Al content x were studied. While two had compositions within the immediate vicinity of the crossover point, the other was assigned to the indirect-gap regime. Results revealed that stimulated emission involved direct recombination.

Research was conducted on the mechanisms responsible for the photoinduced change in the optical properties of semiconducting CdF2 crystals with metastable Ga impurities forming DX centers. A modification of the refractive index of the crystal permits writing of persistent holographic gratings at temperatures reaching 200 K which is considered high for this class of holographic devices. The refractive index change, grating decay and sensitivity features of CdF2:Ga crystals are described.

The electronic passivation of (100) In0.2Ga0.8As-GaAs surface quantum wells was described and compared to the Al0.45Ga0.55As passivation layer using a Ga2O3 molecular beam method. Two-inch semiconductor wafers were designed with the aid of a multiple-chamber ultrahigh vacuum. The insulator passivation produced an internal quantum efficiency similar to that of semiconductor Al0.45Ga0.55 As passivation. In addition, Ga2O3 electronic passivation prevented band bending and simplified device processing.

The results of an ongoing collaborative project between the New Jersey Institute of Technology (NJIT) and SEMATECH on the temperature-dependent emissivity of silicon-related materials and structures are presented in this study. These results have been acquired using a spectral emissometer. This emissometer consists of a Fourier Transform Infra-Red (FTIR) spectrometer designed specifically to facilitate simultaneous measurements of surface spectral emittance and temperature by using optical techniques over the near- and mid-IR spectral range and temperatures ranging from 300 K to 2000 K. This noncontact, real-time technique has been used to measure radiative properties as a function of temperature and wavelength for a wide range of silicon-related materials and structures. The first results of the temperature and wavelength dependent emissivity and hence refractive index of silicon nitride, in the literature, is presented in this study. Index Terms - Emissivity, optical properties, rapid thermal processing, silicon, silicon dioxide, silicon nitride, temperature measurement.

Research was conducted to identify the effects of doping on the resistivity of films and the mobility and concentration of the charge carriers. In this study, the spray-pyrolysis technique is used to deposit thin films of fluorine-doped tin dioxide films on borosilicate glass. Some of the results that were derived from the tests include electron mobility, doping yield, sheet resistance and figure of merit.

The annealing properties, structural damage formation and recrystallization of nitrogen-implanted n-type III-V compound semiconductor InP were investigated. Commercially prepared n-type (100) InP samples doped with sulphur were implanted at room temperature using a 100-kV isotope separator. Results showed that implantation dose influenced the depth of an amorphous layer as well as the type of the vacancy defects. Annealing temperature also affected the type of the vacancy defects.

Time-resolved electro-optic sampling can be applied for probing space charge and thermoelectric fields external to the sample. The approach can be utilized in following the time evolution of surface electric fields resulting from the ultrafast optical generation of excess electron-hole pairs. The use of the technique in externally monitoring the dynamics of carrier heating and transport in semiconductors is demonstrated.

Zn-diffused InP layers were prepared using a sealed tube method. The substrates used were S- and Zn-doped InP crystals. The findings indicate a very sharp diffused/virgin interface in the S-doped crystal and that the diffuse layers are lattice contracted. Moreover, the maximum strain close to the surface is not dependent on the diffusion time and the thickness of the diffused layer increases with time.

A study was conducted on spatial resolution limitations on localized band edge photoluminescence and trap-based luminescence using near-field scanning optical microscopy. The findings indicate that the drift of photogenerated minority carriers to the surface narrows their lateral distribution, resulting in improved spatial resolution. Moreover, a weak dependence on the spatial resolution of the photoluminescence was observed on the tip aperture.

Single heterostructures featuring two GaInP2 layers with different cation sublattice degrees of order were examined using photoluminescence and photoluminescence excitation spectroscopy. The V/III ration was employed to regulate the the degree of order of sample configurations. Results show that that photoluminescence excitation spectroscopy can be used for accurate unicompositional heterostructure characterization.

Metalorganic chemical vapor deposition was employed in preparing heteroepitaxial GaAs layers on Si(100) substrates. The acceptor energy level and valence band structure were found to be influenced by tetragonal distortion caused by mismatches in lattice and thermal expansion coefficient. Results also indicate that a rise in biaxial tensile strain will decrease carbon acceptor binding energy.