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A demonstration of the principles of quantum key distribution (QKD) is performed using a single-photon source in a proof of concept test-bed over a distance of 2 km in standard telecommunications optical fiber. The single-photon source was an optically-pumped quantum dot in a microcavity emitting at a wavelength of 895 nm. Characterization of the QKD parameters was performed at a range of different optical excitation powers. An investigation of the effect of varying the optical excitation power of the quantum dot microcavity on the quantum bit error rate and cryptographic key exchange rate of the system are presented. [ABSTRACT FROM AUTHOR]

Presents information on a study which measured the unnormalized Stokes vector by using a rotating-compensator multichannel ellipsometer. Polarization state of light reflected from specular and textured SnO2: F films; Experimental details; Results and discussions.

Presents a study which calculated the atomic depth distribution in solids produced by high-speed ion bombardment using the concept of the effective displacement volume of an atom. General equations used; Constraints on variation of the effective displacement volume with composition; Overview of an extensive survey of binary metal alloys.

Studies the annealing effect on porosity of amorphous hydrogenated carbon films using a quartz crystal microbalance. Background to the study; Experimental procedures; Results and discussion.

Presents a study that investigated the reliability of the diffusion approximation for the ballistic relocation function in atomic mixing by ion beams. Information on mixing equations; Numerical results; Conclusion.

Presents a study which reported the results of ellipsometry measurements performed during the growth of hydrogenated amorphous silicon thin films on crystalline silicon substrates. Formation of low-density microstructure in the initial stages of growth; Effect of sputtering on the glow-discharge decomposition of gases; Discussion on the pseudodielectric function trajectories.

Presents information on a study which extended in situ ellipsometry characterization of the nucleation and microstrucutral evolution of amorphous silicon (a-Si:H) to the effect of deposition parameters on these processes. Details about the structural evolution of a-Si:H; Important aspects of the ellipsometer/glow-discharge reactor system; General features of in situ trajectories.

Presents a study which examined the effect of substrate microstructure on the growth habit of high-quality hydrogenated amorphous silicon. Experimental details; Results and discussion; Conclusion.

Presents information on a study that examined the growth and microstructure of α-Si:H/α-SiN [subx] :H heterojunctions. Experimental details; Results and discussion on the study; Conclusions.

Presents information on a study which analyzed the in situ ellipsometry measurements taken during the deposition of hydrogenated amorphous silicon on crystalline silicon substrates in a convention rf glow-discharge apparatus. Nucleation behavior of hydrogenated amorphous silicon; Experimental details; Results and discussion; Conclusions.

Presents the results of the application of photoresponse techniques to the study of the transport of electrons past an energy barrier. Investigations of electron transport through gallium arsenide/aluminum arsenide heterostructures; Model for the absorption of the light in the structures used; Change in the band gap as compared to the shift in the peak position in the voltage spectrum of the second sample.

Examines the optical properties of ion-beam-sputtered silicon and germanium using spectroscopic ellipsometry. Discrepancies between the structure of the p-silicon deduced from Raman and ellipsometry spectra; Significance of thin-film polycrystalline silicon; Psuedodielectric functions for ion-beam-deposited silicon prepared at different substrate temperatures.

Analyzes the structure of a hydrogenated amorphous silicon based n-1 two-layer system using spectroscopic ellipsometry measurements. Details on the experiment; Data analysis; Results of the study.

Presents a study which examined the optimization and analysis of solar selective surfaces with continuous and multilayer profiles. Theory and computation method; Results and discussion; Conclusions.

Studies pressure relaxation in atomic mixing and preferential sputtering. Determination of relocation without relaxation; Measurement of relaxation current; Analysis of the motion of the surface.

Reports on the application of real time spectroscopic ellipsometry to characterize the nucleation of diamond on c-silicon by tungsten filament-assisted chemical vapor deposition (CVD). Stages of diamond growth by filament-assisted CVD; Preparation of the diamond; Information on the structural model and parameters deduced in a linear regression analysis of the final spectra.

Provides information on a study which proposed a field-effect transistor structure based on strain-induced polarization charges. Discussion of the pseudomorphic growth of a barrier layer on a substrate oriented in a polar direction; Observation concerning polarization and piezoelectric effect; Forms at the heterointerface to screen the polarization charges.

Probes the evolution of surface roughness over a wide range of film thickness during the growth of glow discharge hydrogenated amorphous silicon (a-Si:H) using in situ ellipsometry. Differences in the resulting film properties; Factor to which the columnar morphology observed for SiH[sub4]:argon films is attributed; Description of the pseudodielectric function.

Responds to Andrew Vogt's comments on the article in volume 34 of the 'Journal of Mathematical Physics,' on the differentiability of the position probability density rho(x/t). Oversight in the constraint on rho(x/t); Error arising from an inappropriate simplification in assuring boundary conditions.

It is shown that imposition of the requirement of differentiability on a probability distribution imposes a structure on the probability formalism having the appearance of physical theory. Both the classical and quantum mechanical descriptions for the motion of a single point particle as consequences of describing the motion in terms of a differentiable probability density are exhibited. It is shown that the particle must appear as acted upon by a force having the form of the Lorentz force. [ABSTRACT FROM AUTHOR]

Presents a computer simulation of a one-dimensional particle migration by local hopping of Chandrasekhar type with no local bias. Concept of local particle traffic; Cases of reflecting and absorbing boundaries; Specification and evaluation of the hopping model.

A unique rapid-scanning ellipsometer employing a rotating polarizer optical configuration and a multichannel detector for a 1.5–4.5 eV spectral range, has been developed recently for real time studies of film growth and surfaces. This is a new application of the photodiode array-based optical multichannel detector that entails waveform analysis of the incident irradiance at each photon energy. For accurate ellipsometric spectra {ψ(hν),Δ(hν)}, the raw data in the form of photon counts, integrated over four or more equal sectors of polarizer rotation, must be corrected for systematic errors originating from the detection system. Simple procedures are described to characterize and correct for the most significant errors including detection system nonlinearity, image persistence, and scattered stray light in the spectrograph/detector enclosure. [ABSTRACT FROM AUTHOR]

In a typical reflection ellipsometry experiment, one characterizes the polarization state change that a polarized light beam undergoes upon reflection from a specular surface. This measurement provides ρ≡rp/rs, where rp and rs are the complex amplitude reflection coefficients of the surface for p- and s-polarized waves. Nearly 15 years have passed since the development of automatic ellipsometers along with the detailed calibration, error analysis, and data reduction procedures to be used with them. More specifically, these powerful instruments permit (1) determination of bulk dielectric functions and nondestructive depth profiling of static multilayered materials through measurements as a function of photon energy and (2) characterization of dynamic surfaces in adverse environments through measurements as a function of time at fixed photon energy. In the 15 intervening years, the major research thrusts in ellipsometry have been the exploitation of these instruments in materials and process characterization in diverse areas of materials science and electrochemistry. One of the simplest and most popular automatic ellipsometers is a photometric instrument in which one or more of the optical elements (polarizer, compensator, and/or analyzer) is designed to rotate continuously. In this article, the major developments in rotating element ellipsometry are reviewed since the first report of an automatic rotating analyzer instrument by Cahan and Spanier in 1969. The topics covered include rotating element configurations, calibration, characterization of errors and imperfections, absolute accuracy, data reduction, precision, and a review of the real-time applications accessible to these instruments. The sections on calibration, errors, and data reduction include new material and are written from a practical standpoint to assist in instrumentation setup and troubleshooting. The development and improvement of next-generation rotating element instruments that... [ABSTRACT FROM AUTHOR]

The dielectric function of Ag nanoparticle films, deduced from an analysis of in situ real-time spectroscopic ellipsometry (RTSE) measurements, is found to evolve with time during deposition in close consistency with the film structure, deduced in the same RTSE analysis. In the nucleation regime, the intraband dielectric function component is absent and plasmon polariton behavior dominates. Only at nuclei contact, does the intraband amplitude appear, increasing above zero. Both intraband and plasmon amplitudes coexist during surface smoothening associated with coalescence. The intraband relaxation time increases rapidly after surface smoothening is complete, also in consistency with the thin film structural evolution. [ABSTRACT FROM AUTHOR]

CdS/CdTe solar cells were nonuniformly doped at the backsurface of the CdTe with Cu evaporated through a shadow mask. Spatially resolved electroluminescence measurements showed strong correlation of emission intensity with the Cu pattern for all photon energies. Photoluminescence (PL) measurements performed on the exact same region showed no correlation with the Cu pattern when integrated over all energies. However, lower energy PL (located in a broad defect-related band) was slightly more intense in Cu-doped regions, whereas the intensity of PL from shallower states was slightly greater in undoped regions. These small differences in spectra were discernable only with the patterned doping and spatially resolved characterization used here. [ABSTRACT FROM AUTHOR]

Studies near-field scanning optical nanolithography using amorphous silicon photoresists. Production of films that are stable over several days; Patterns with line heights equal to the original film thickness.

The dielectric functions of 0.5–1.5-μm-thick Zn1-xCdxSe (0≤x≤0.34) epilayers on (100) GaAs were measured by spectroellipsometry (SE) over the photon energy range 1.5≤E≤5.3 eV. These spectra were parameterized using the Sellmeier and Lorentz equations for photon energies below and above the fundamental gap region, respectively. We have demonstrated the usefulness of this parameterization in analyses of SE data collected on a ZnSe heterostructure and a Zn1-xCdxSe quantum well that provide accurate layer thicknesses and compositions. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We present the results of the application of photoresponse techniques to the study of the transport of electrons past an energy barrier. In this study, the barrier was provided by a thin layer of AlAs sandwiched between GaAs layers. The experiment measured the voltage resulting from the migration of optically excited electrons from one side of the barrier to the other. The voltage is measured as a function of the wavelength of the incident light. We also present the results of calculations which explain the nature of the observed spectra and how they change when the thickness of the top layer (the illuminated side) of GaAs is changed. [ABSTRACT FROM AUTHOR]

We report the first observation of inelastic tunneling in electronic transport perpendicular to a thin AlAs layer sandwiched between two GaAs layers. Temperature dependent I-V, first derivative (dI/dV), and second derivative (d2I/dV2) measurements were made on AlAs/GaAs double heterojunctions for a range of AlAs layer thicknesses and dopings. For p-type AlAs barriers current transport at 4.2 K was due to tunneling, and reproducible structure was seen in the second derivative spectrum. This structure was associated with the inelastic excitation of AlAs optical phonons and with a density-of-states effect caused by optical phonon-electron coupling in the GaAs. A different second derivative spectrum which also exhibited reproducible structure was obtained for n-type AlAs layers. Several possible explanations for these differences are proposed. [ABSTRACT FROM AUTHOR]

In situ ellipsometry provides monolayer sensitivity to the reaction of B2H6:SiH4 doping gas mixtures with p- and i-type plasma-enhanced chemical vapor deposited (PECVD) amorphous silicon (a-Si:H) surfaces at 180 and 250 °C. This low-temperature reaction, leading to the slow growth (1–3 Å/min) of a-Si:H:B by CVD (without plasma excitation), requires a clean a-Si:H surface and both B2H6 and SiH4 in the doping gas. We suggest that the high B content of CVD a-Si:H:B at p-i and i-p interfaces and on the film-coated regions of single-chamber reactors, may contribute to poor interface characteristics and residual contamination in devices. [ABSTRACT FROM AUTHOR]

Hydrogenated amorphous carbon film growth in diamond-like and polymer-like forms has been studied by in situ ellipsometry. The experiments provide accurate values of the optical functions, thickness, and deposition rate in real time. Reactions between the substrate and the gas phase species or film in the initial stages of growth, inaccessible to ex situ probes, have been detected with monolayer resolution. Monolayer changes in near-surface bonding have also been detected. [ABSTRACT FROM AUTHOR]

The effect of substrate temperature (Ts) on the initial nucleation of hydrogenated amorphous silicon (a-Si:H) prepared by glow discharge has been studied using an in situ ellipsometry probe. Evidence in the ellipsometry data for clustering of Si–Si bonds at nucleation centers, for films prepared with Ts ∼250 °C, gradually disappears as Ts is reduced below ∼200 °C. This indicates that the clustering process accompanies defect reduction during growth commonly observed in glow discharge a-Si:H as Ts is increased. For Ts >200 °C, a sufficiently high surface mobility may enable the depositing species to bind at lower energy sites, thus explaining the observed results. [ABSTRACT FROM AUTHOR]

We present the results of a study of the transport of optically excited carriers perpendicular to weakly coupled GaAs/AlAs multiple quantum wells imbedded in the depletion region of a p-i-n photodiode. At temperatures above 120 K the photocurrent was thermally activated. For lower temperatures the photocurrent decreased as temperature was increased. Wavelength-dependent negative differential resistance regions were present in the reverse bias region of the photoexcited current voltage (I-V) curve as a result of the Stark shifts of the lowest energy heavy hole (h1) and light hole (l1) excitons. Additional wavelength independent structure was also visible in the photoexcited I-V curves. [ABSTRACT FROM AUTHOR]

In situ ellipsometry experiments have been used to probe the structural changes that occur in the initial stages of the growth of microcrystalline silicon ( μc-Si) on single-crystal Si substrates. The initial nucleation of μc-Si appears to occur at well-dispersed sites and ∼100 Å of material with significantly different optical properties than the bulk is buried at the film/substrate interface. The different optical structure of this interface layer is attributed to voids which are trapped when crystalline nuclei merge. These results are contrasted with recent data for hydrogenated amorphous silicon which show that nuclei converge after about 50 Å, leaving material with bulklike optical properties at the substrate interface. [ABSTRACT FROM AUTHOR]

We report the first observations of resonant tunneling in electronic transport perpendicular to two AlAs layers separated by a GaAs quantum well in GaAs/AlAs heterostructures grown by metalorganic chemical vapor deposition. Resonant tunneling can be observed as inflections in the 1-V curves at room temperature. These inflections become more pronounced as the temperature is reduced, until negative differential resistance regions become visible for temperatures below 260 K. At low temperatures, the I-V curves not only reveal two large negative resistance regions corresponding to the first energy level in the GaAs quantum well but also a structure which shows evidence of resonant tunneling through the second and possibly the third energy states in the well. Second derivative (d²1/dV²) measurements confirm the existence of the resonances seen in the I-V curves. [ABSTRACT FROM AUTHOR]

Long-range surface plasmons traveling on thin metal films have demonstrated promising potential in subwavelength waveguide applications. In work toward device applications that can leverage existing silicon microelectronics technology, it is of interest to explore the propagation of surface plasmons in a metal-oxide-semiconductor geometry. In such a structure, there is a high refractive index contrast between the semiconductor (n≈3.5 for silicon) and the insulating oxide (typically n≈1.5-2.5). However, the introduction of dielectrics with disparate refractive indices is known to strongly affect the guiding properties of surface plasmons. In this paper, we analyze the implications of high index contrast in 1D layered surface plasmon structures. We show that it is possible to introduce a thin dielectric layer with a low refractive index positioned next to the metal without adversely affecting the guiding quality. In fact, such a configuration can dramatically increase the propagation length of the conventional long-range mode. While this study is directed at silicon-compatible waveguides working at telecommunications wavelengths, this configuration has general implications for surface plasmon structure design using other materials and operating at alternative wavelengths. [ABSTRACT FROM AUTHOR]

Both the origins of the high open circuit voltages (VOC) in amorphous silicon solar cells having p layers prepared with very high hydrogen dilution and the physical structure of these optimum p layers remain poorly understood topics, with several studies offering conflicting views. This work attempts to overcome the limitations of previous studies by combining insights available from electronic measurements, real time spectroscopic ellipsometry, atomic force microscopy, and both high-resolution transmission electron microscopy (TEM) and dark field TEM of cross sections of entire solar cells. It is found that solar cells fabricated with p layers having a low volume fraction of nanocrystals embedded in a protocrystalline Si:H matrix possess lower recombination at the i/p interface than standard cells and deliver a higher VOC. The growth of the p layers follows a thickness evolution in which pure protocrystalline character is observed at the interface to the i layer. However, a low density of nanocrystallites nucleates with increasing thickness. The advantages offered by the protocrystalline character associated with the amorphous phase of the mixed-phase (amorphous+nanocrystalline) p layers prepared with excess H2 dilution account for the improved VOC of the optimum p layers. In this model, the appearance of a low volume fraction of nanocrystals near the top transparent conductor interface is proposed to be incidental to the high VOC. [ABSTRACT FROM AUTHOR]

We critically examine how two processing steps commonly applied in the preparation of cadmium telluride (CdTe)-based solar cells, i.e., the cadmium chloride treatment and the subsequent stepwise bromine/methanol wet etching process, impact the structural and optical properties of polycrystalline CdTe thin-films. In particular, drawing upon a conjuncture of photothermal deflection spectroscopy and spectroscopic ellipsometry experimental results, we determine the spectral dependence of the optical absorption coefficient, α(E), over the photon energy range from 1.1 to 2.0 eV for samples of rf sputtered (RFS) and close space sublimation (CSS) CdTe. The impact of these processing steps on shaping the grazing incidence x-ray diffraction pattern is also examined. We extend the analysis to devices through interpretation of the spectral dependence of the external quantum efficiency associated with two cadmium chloride treated CdTe-based solar cells. The cells are comparably prepared with the exception of the absorber, one by RFS and the other by CSS. Through the use of our results for the thin-film CdTe optical functions and a model for the solar cell multilayer structure, we simulate the resultant external quantum efficiency spectrum. Through a critical contrast with the corresponding solar cell acquired experimental results, we glean insights into the carrier trapping and recombination processes that occur within the two types of CdTe absorbers. [ABSTRACT FROM AUTHOR]

Describes a numerical iterative scheme which can be used in solving inverse problems encountered in the application of the ac field measurement (acfm) technique for sizing surface breaking cracks in metals. List of methods in detecting metal flaw; Distinguishing feature of acfm; Discussion on the relationship between crack depth and surface potentials.

In situ and ex situ characterization methods have been applied to investigate the properties of (Ag,Cu)InSe2 (ACIS) thin films. Data acquired from real time spectroscopic ellipsometry (RTSE) experiments were analyzed to extract the evolution of the nucleating, bulk, and surface roughness layer thicknesses. The evolution of these layer thicknesses suggests a transition from Volmer-Weber to Stranski-Krastanov type behavior when Cu is replaced by Ag. The complex dielectric functions of ACIS at both deposition and room temperature as a function of film composition were also extracted from the RTSE data, enabling parameterization of the alloy optical properties. [ABSTRACT FROM AUTHOR]

Silver nanoparticle films were deposited by sputtering at room temperature and were annealed while monitoring by real time spectroscopic ellipsometry (SE). The nanoparticle dielectric functions (0.75 eV-6.5 eV) obtained by SE were modeled using Lorentz and generalized oscillators for the nanoparticle plasmon polariton (NPP) and interband transitions, respectively. The nanoparticle melting point could be identified from variations in the oscillator parameters during annealing, and this identification was further confirmed after cooling through significant, irreversible changes in these parameters relative to the as-deposited film. The variation in melting point with physical thickness, and thus average nanoparticle diameter, as measured by SE enables calculation of the surface energy density. [ABSTRACT FROM AUTHOR]

A multichannel ellipsometer in the dual rotating-compensator configuration has been developed for applications in real time Mueller matrix spectroscopy of anisotropic surfaces and thin films. The sequence of optical elements for this instrument configuration can be denoted PC[sub 1r](5ω)SC[sub 2r](3ω)A, where P, S, and A represent the polarizer, sample, and analyzer. In this sequence, C[sub 1r] and C[sub 2r] represent the first and second compensators, rotating with angular frequencies of 5ω and 3ω, respectively, where ω=π/T[sub C] is the base angular frequency (corresponding to 2 Hz) and T[sub C]=0.25 s is the fundamental optical period. The instrument can provide 170 point spectra over the wavelength range from 235 nm (5.3 eV) to 735 nm (1.7 eV) in all 16 elements of the unnormalized Mueller matrix with minimum acquisition and repetition times of T[sub C]=0.25 s. In this study, instrumentation calibration procedures are demonstrated in the transmission geometry without a sample, including (i) alignment of the two MgF[sub 2] zero-order biplate compensators, (ii) determination of the retardance and phase spectra for the compensators, (iii) determination of the offset angles for the optical elements, and (iv) characterization of the spectral response function of the ellipsometer. Calibration procedure (iv) allows the (1,1) element of the transmission Mueller matrix to be determined; thus the unnormalized Mueller matrix can be obtained. The dual rotating-compensator multichannel ellipsometer is assessed with respect to its performance in transmission without a sample, and is then applied in the transmission geometry to study anisotropy, depolarization, and light scattering effects for a MgF[sub 2] helicoidally sculptured thin film on a glass substrate. Numerous future applications of this instrument are anticipated for real time analysis of complex surfaces and thin films in the reflection geometry as well. [ABSTRACT FROM AUTHOR]

In situ spectroscopic ellipsometry was applied to measure the dielectric functions &eh; of polycrystalline CdTe thin films prepared by magnetron sputtering. The observable critical point (CP) energies determined for the films in best fits to d2&eh;/dE2 are shifted relative to those for single crystal CdTe. The energy shift of the critical point designated as En is attributed to in-plane stress X with linear stress coefficient CX(En). By analyzing these shifts, it was found that stress (1) builds with thickness in as-deposited films, (2) relaxes with increasing substrate temperature at fixed thickness, and (3) is relaxed uniformly in CdCl2 treated films. [ABSTRACT FROM AUTHOR]

The dielectric functions [variant_greek_epsilon] of polycrystalline CdS and CdTe thin films sputter deposited onto Si wafers were measured from 0.75 to 6.5 eV by in situ spectroscopic ellipsometry. Differences in [variant_greek_epsilon] due to processing variations are well understood using an excited carrier scattering model. For each sample, a carrier mean free path λ is defined that is found to be inversely proportional to the broadening of each of the band structure critical points (CPs) deduced from [variant_greek_epsilon]. The rate at which broadening occurs with λ-1 is different for each CP, enabling a carrier group speed υg to be identified for the CP. With the database for υg, [variant_greek_epsilon] can be analyzed to evaluate the quality of materials used in CdS/CdTe photovoltaic heterojunctions. [ABSTRACT FROM AUTHOR]

To take into account the presence of multiple light-induced defect states in hydrogenated amorphous silicon (a-Si:H) the evolution of the entire spectra of photoconductive subgap absorption, α(hν), has been analyzed. Using this approach two distinctly different light-induced defect states centered around 1.0 and 1.2 eV from the conduction band edge are clearly identified. Results are presented on their evolution and respective effects on carrier recombination that clearly point to the importance of these states in evaluating the stability of different a-Si:H solar cell materials, as well as elucidating the origin of the Staebler–Wronski effect. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A near-field scanning optical microscope was used in collection mode to generate spatially resolved maps of the first derivative with respect to operating current of power emission from vertical-cavity surface-emitting lasers (VCSELs). This technique is highly sensitive to the formation of new modes and can be used to identify mode cutoff points. An example of the usefulness of this technique is demonstrated as we estimate the index of refraction profile of the VCSEL under study at the single mode cutoff point. This profile is a primary feature of the waveguiding characteristics of such lasers. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Real-time spectroscopic ellipsometry with an ultraviolet-extended spectral range (1.5-6.5 eV) has been applied to investigate the sputter deposition of boron nitride (BN) thin films with high cubic content in terms of a two-layer optical model. In this model, the inner and outer layers represent sp[sup 2]- and sp[sup 3]-bonded BN (hBN and cBN), respectively. The thickness evolution of the two layers as well as their dielectric functions over the extended spectral range have been determined. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have developed a Kramers-Kronig consistent analytical expression to fit the measured optical functions of hydrogenated amorphous silicon (a-Si:H) based alloys, i.e., the real and imaginary parts of the dielectric function (∈[sub 1], ∈[sub 2]) (or the index of refraction n and absorption coefficient α) versus photon energy E for the alloys. The alloys of interest include amorphous silicon-germanium (a-Si[sub 1-χ]Ge[sub χ] :H) and silicon-carbon (a-Si[sub 1-χ]C[sub χ] :H), with band gaps ranging continuously from ∼1.30 to 1.95 eV. The analytical expression incorporates the minimum number of physically meaningful, E independent parameters required to fit (∈1, ∈[sub 2]) versus E. The fit is performed simultaneously throughout the following three regions: (i) the below-band gap (or Urbach tail) region where a increases exponentially with E, (ii) the near-band gap region where transitions are assumed to occur between parabolic bands with constant dipole matrix element, and (iii) the above-band gap region where (∈[sub 1], ∈[sub 2]) can be simulated assuming a single Lorentz oscillator. The expression developed here provides an improved description of ∈[sub 2] (or α) in the below-band gap and near-band gap regions compared with previous approaches. Although the expression is more complicated analytically, it has numerous applications in the analysis and simulation of thin film a-Si:H based p-i-n and n-i-p multilayer photovoltaic devices. First, we describe an approach whereby, from a single accessible measure of the optical band gap, the optical functions can be generated over the full solar spectrum for a sample set consisting of the highest quality intrinsic a-Si:H based alloys prepared by plasma-enhanced chemical vapor deposition using the principle of maximal H[sub 2] dilution. Second, we describe quantitatively how such an approach can be modified for sample sets consisting of lower quality... [ABSTRACT FROM AUTHOR]

The c[sub 0] lattice parameter, band gap, and photoluminescence spectra of n-type 0.9 μm thick In[sub x]Ga[sub 1-x]N films with x=0, 0.045, 0.085, and 0.140 were examined. The c[sub 0] lattice parameter followed Vegard’s law using c[sub 0]=0.5185 nm for GaN and c[sub 0]=0.569 nm for InN. Band gap measurements by photocurrent spectroscopy fit well with data published by one other research group, with the combined set being described by the equation E[sub g]=3.41-7.31x+14.99x[sup 2] for 0≤x≤0.15. Photoluminescence measurements with a pulsed nitrogen laser showed a peak well below the measured band gap, as well as significant luminescence above the measured band gap. The above-gap luminescence appears to be due to band filling by the high intensity laser pulses. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]