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The effect of doping with oxygen the microcrystalline silicon-germanium absorber layer of singlejunction p-i-n solar cells has been studied. In parallel, the absorber layer quality was measured by depositing absorber layers directly on glass and measuring their electrical properties. By doping the absorber layer with the optimum oxygen concentration (about 1:4 × 1019 cm–3), an increase in short-circuit current density of almost 4 mA/cm2 was achieved in 3 μm thick p-i-n solar cell. This effect is attributed to the oxygen doping compensating the space charges caused by the germanium dangling bonds rather than the direct defect passivation, as no drastic change in layer quality was measured. [ABSTRACT FROM AUTHOR]

Hydrogenated microcrystalline silicon films (μc-Si:H) deposited at high deposition rates (∼2 nm/s) by means of the very-high-frequency (VHF) deposition technique in the high pressure depletion regime have been integrated into single junction p-i-n solar cells. It is demonstrated that μc-Si:H solar cells can be optimized using a twofold approach. First the bulk properties, deposited under steady-state plasma conditions, are optimized by monitoring the presence of crystalline grain boundaries in μc-Si:H. These hydrogenated crystalline grain boundaries can easily be detected via the crystalline surface hydrides contribution to the narrow high stretching modes by infrared transmission spectroscopy. The crystalline grain boundaries suffer from postdeposition oxidation which results in a reduced red response of the solar cell. The absence of these crystalline surfaces in an as-deposited μc-Si:H matrix reflects the device grade microcrystalline bulk material. Second, the prevention of silane backdiffusion from the background during the initial growth is a necessity to deposit a uniform μc-Si:H phase over the entire film thickness. The initial growth is optimized while preserving the optimized bulk properties deposited under steady-state conditions, using initial profiling of plasma parameters such as the silane flow and the VHF power density. Solar cell devices with efficiency of 8.0% at a μc-Si:H deposition rate of 2.0 nm/s are obtained using the presented approach. [ABSTRACT FROM AUTHOR]

Capacitively coupled very-high-frequency hydrogen plasmas have been systematically diagnosed in a wide range of a gas pressure from 5 mTorr to 10 Torr. The plasma parameters, ion species, and ion energy distributions (IEDs) are measured using a Langmuir probe, optical emission spectroscopy, and energy filtered mass spectrometer. The measurement results show that the ion species in a hydrogen plasma is determined from ionization channels and subsequent ion-molecule reactions. The ions are dominated by H2+ at a less-collisional condition of ≤20 mTorr, whereas those are dominated by H3+ at a collisional condition of >=20 mTorr. The IED is determined by both the sheath potential drop and ion-neutral collisions in the plasma sheath. The IED is broadened for a collisional sheath at >=0.3 Torr and the ion bombardment energy is lowered. For high-pressure discharge operated at ≈10 Torr, plasmas are characterized by a low electron temperature of ≈0.8 eV and a low ion bombardment energy of ≤15 eV. [ABSTRACT FROM AUTHOR]

Transparent conductive Zr-doped In2O3 (In2-2xZr2xO3) films were deposited on glasses by sputtering method. High mobility of over 80 cm2/V s was achieved under a carrier density of 1.3-2.9×1020 cm-3 at Zr concentrations (x) of 0.014–0.022, and the film at x=0.022 showed the lowest resistivity of 2.6×10-4 Ω cm. Reflecting the high mobility and the low carrier density, the transparency extended from the visible to the near-infrared (NIR) wavelength region with reduced magnitude of the free-carrier absorption. The results indicate that Zr-doped In2O3 films have a performance advantage for applications that require high conductivity and transparency in NIR wavelength region. [ABSTRACT FROM AUTHOR]

We report on comparative studies of transparent conductive Ti-, Zr-, and Sn-doped In2O3 using a combinatorial approach. In2-2xMe2xO3 (Me:Ti, Zr, Sn) composition-spread epilayers (0≤x≤0.1) were fabricated on yttria-stabilized zirconia substrates using the combinatorial pulsed laser deposition technique, and structural, optical, and electrical properties for each composition were systematically investigated. In2-2xTi2xO3 (0.003≤x<0.01) and In2-2xZr2xO3 (0.003≤x<0.05) exhibited superior transparency in the near infrared wavelength region compared to In2-2xSn2xO3 without compromising the conductivity. The results are discussed in terms of scattering centers of electrons from temperature dependence of Hall mobility and the relationship between the values of the room temperature Hall mobility and carrier concentration. [ABSTRACT FROM AUTHOR]

In2O3 heteroepitaxial layers of improved surface morphology and mobility were obtained by pulsed-laser-deposition method supplying proper oxygen to indium ratio on the growing surface, combined with the suppression of thermal decomposition of In2O3 layers. In situ monitoring of reflection high-energy electron diffraction patterns and ex situ monitoring of growth rate of the epilayers grown under different oxygen pressures and growth temperatures revealed that thermal decomposition occurred during the high-temperature growth and the use of significant oxygen pressure could suppress decomposition allowing for an increase in obtainable growth temperatures. As a result of the decomposition control and growth optimization, undoped In2O3 epilayers exhibited atomically flat surfaces, improved Hall mobility of 110 cm2/V s, and carrier density of 6.6×1018 cm-3. The influences of growth and postgrowth conditions on the electrical properties of epilayers were investigated based on charged and neutral impurity scattering models. The origins of the scattering centers of electrons were considered to be the same for both epilayers grown under different growth conditions (oxygen pressure and growth temperature) and annealed in reduced atmosphere after growths, and ionized impurity scatterings such as oxygen vacancy are the most probable candidates; however, postgrowth annealing process under 1 atm oxygen was considered to generate another scattering center, leading to the decrease in both mobility and carrier density. [ABSTRACT FROM AUTHOR]

The interaction of HCl with the D2O-ice surface has been investigated in the temperature range 15–200 K by utilizing time-of-flight secondary ion mass spectroscopy, temperature-programmed desorption, and x-ray photoelectron spectroscopy. The intensities of sputtered H+(D2O) and Cl- ions (the H+ ions) are increased (decreased) markedly above 40 K due to the hydrogen bond formation between the HCl and D2O molecules. The HCl molecules which form ionic hydrates undergo H/D exchange at 110–140 K and a considerable fraction of them dissolves into the bulk above 140 K. The neutral hydrates of HCl should coexist as evidenced by the desorption of HCl above 170 K. They are incorporated completely in the D2O layer up to 140 K. The HCl molecules embedded in the thick D2O layer dissolve into the bulk, and the ionic hydrate tends to segregate to the surface above 150 K. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

TOF-SIMS is used to investigate the interactions between D[sub 2]O and hydrophobic molecules, such as CH[sub 4], CH[sub 3]F, CH[sub 2]F[sub 2], CHF[sub 3], and CF[sub 4], at cryogenic temperatures (15 K). By irradiation with a 1.5-keV He[sup +] beam, the D[sup +](D[sub 2]O)[sub n] ions are ejected efficiently from the D[sub 2]O nanoclusters physisorbed on the CF[sub 4] layer due to Coulomb explosion: the ion yields are by about two orders of magnitude higher than those from a thick D[sub 2]O layer via the kinetic sputtering. The D[sup +](D[sub 2]O)[sub n] yields decrease on the CH[sub n]F[sub 4-n] layer with increasing the number of the C–H group. This is because the Coulombic fission is quenched due to the delocalization of valence holes through the C–H...H–C and C–H...D[sub 2]O contacts. A pure D[sub 2]O film is hardly grown on the CH[sub 4] layer as a consequence of intermixing whereas the D[sub 2]O molecules basically adsorb on the surfaces of fluoromethanes, suggesting the attractive (water-repellent) interactions in the C–H...D[sub 2]O (C–F...D[sub 2]O) contacts. The C–H...O bond behaves like a conventional O–H...O hydrogen bond as far as the collision-induced proton transfer reaction is concerned. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The interactions between condensed molecules at cryogenic temperatures (15–200 K) have been investigated on the basis of secondary ion mass spectrometry. It is demonstrated that the protonated molecular ions, emitted via the proton transfer reactions, provide us unique information about the reorganization of hydrogen-bonded molecules. From the CH[sub 3]OH molecules adsorbed on the D[sub 2]O–ice surface, the D[sup +](CH[sub 3]OH) ions are sputtered predominantly in the temperature range between 100 and 150 K since most of the CH[sub 3]OH molecules are bound to the D[sub 2]O layer via hydrogen bonds. A rapid and almost complete H/D exchange, yielding the D[sup +](CH[sub 3]OD) species, occurs above 150 K due to the enhanced mobility of the surface D[sub 2]O molecules. Up to the desorption temperature of 180 K, a considerable amount of methanol exists on the surface without mixing with the heavy-water layer due to hydrophobicity of the methyl group. On the methanol–ice surface, the adsorbed D[sub 2]O molecules form hydrogen bonds preferentially with the CH[sub 3]OH molecules and tend to be incorporated in the thin-layer bulk of methanol above 120 K. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We discuss results of surface photovoltage (U) measurements for d = 10 µm thick layers of undoped hydrogenated microcrystalline silicon (µc-Si:H). By applying excitation with low energetic photons (down to 1.1 eV), i.e., with small absorption coefficient a and a large penetration depth α[sup -1], a photovoltage peak appears on a curve U= U(α). This peak is located at α...d[sup -1] and its occurrence depends critically on the substrate material. The peak is present in a µc-Si:H film grown on p + crystalline silicon (c-Si), on the other hand it is missing in the µc-Si:H samples grown on n[sup +] c-Si or ZnO film. We present a mathematical model that enables us to link this peak to photocharge separation in the bottom space charge region at the interface µc-Si:H/substrate. Besides the magnitude of the ambipolar carrier diffusion length L, a parameter particularly critical for the occurrence of the peak turns out to be the ratio n of reverse saturation current densities of the two diodes representing surface and bottom space charge regions. The peak can be observed only when n is below a certain threshold value n[sub th]. In the simplified case when d/L ... 1 and when the thicknesses of the upper and lower depletion layers can be neglected, we have found n[sub th] ≈ 0.135 or 1, depending on the orientation of the top and bottom barriers to each other. However, the magnitude of the peak increases exponentially with further lowering of n. Therefore, the surface photovoltage method is suitable not only for evaluating the minority carrier diffusion length L, but also for detecting the occurrence and properties of the bottom space charge region in thin film solar cells. [ABSTRACT FROM AUTHOR]

Presents an examination of the dependence of window effects on the aluminum content of a window layer in high-power AlGaAs window structure layers. Experimental details; Results; Discussion.

Examines nonradiative recombination centers in undoped (Al[subx]Ga[sub1-x])[sub0.5]In[sub0.5] by metalorganic vapor phase epitaxy using transient capacitance spectroscopy. Details of the experiment; Information on the electron trapping centers; Method used to study the interaction of a deep energy level with minority carriers.

Presents a study that investigated theoretically and experimentally the gain characteristics in quantum-well lasers. Use of Hakki and Paoli's method in measuring the polarization gain-current characteristics of (111)- and (100)-oriented gallium arsenide/aluminum gallium arsenic single-quantum-well lasers; Details on the experimental results of polarization-dependent spontaneous emission; Conclusion of the study.

Focuses on a study that investigated the energy-band structure of aluminum arsenide and gallium arsenide short-period superlattices by using photoluminescence excitation spectroscopy. Sample preparation; Results and discussion; Conclusion.

This paper describes an iron-loss analysis of permanent-magnet synchronous motor (PMSM) taking into account lamination of iron core by a finite-element method (FEM) with a homogenization method. The detailed modeling of the laminated structure by the FEM with gap elements and double nodes requires a huge number of elements, which results in the limitation of the problem size. In order to reduce the computational costs, we apply the homogenization method to iron-loss analyses of a skewed interior PMSM and a surface permanent-magnet motor with overhanging magnet. For the clarification of the effectiveness, the homogenization method is compared with the detailed modeling from the viewpoints of computational costs and accuracy. As a consequence, it is verified that the homogenization method can analyze magnetic fields in a laminated iron core of a practical electric machine within acceptable computational costs. [ABSTRACT FROM AUTHOR]

This article proposes an effective computational approach to design optimization of an outer-rotor type permanent magnet synchronous motor. As usual, because of the complicated rotor configuration and the complex magnetic saturation effects, it is difficult to design the lightweight permanent magnet synchronous motor structure that makes good use of reluctance torque within an acceptable CPU time. In this article, we adopt the finite element method as a magnetic field analysis method and the genetic algorithms as a search method. Furthermore, the response surface methodology, which enables us to evaluate the objective physical quantities in a much shorter time, is introduced into the above methods in the proposed approach. This optimization approach results in an overall increase in the optimization speed, that is, substantial CPU time reduction in comparison with the case of a conventional one. Some numerical results that demonstrate the validity of the proposed approach are also presented. [ABSTRACT FROM AUTHOR]

Examines high-power cw operation in a (111)-oriented gallium arsenide/AlGaAs single-quantum-well lasers prepared by molecular beam epitaxy (MBE). Elimination of the slip line defects in the MBE-grown wafers; Layer sequence of laser diodes; Output-current characteristics of the devices with the aluminum arsenide mole fraction.

Presents a study which investigated high-purity aluminum gallium arsenide grown by molecular beam epitaxy using a superlattice buffer layer. Method of the study; Results and discussion; Conclusion.

We present umbrella-shaped diamond microstructures with metal mirrors at the bottom in order to improve the amount of collected photons from nitrogen vacancy centers. The metal mirrors at the bottom are self-aligned to the umbrella-shaped diamond microstructures which are selectively grown through holes created on a metal mask. By the finite-difference time-domain simulations, we found that the umbrella-shaped microstructures, which have an effect similar to solid immersion lens, could collect photons more efficiently than bulk or pillar-shaped microstructures. Improvement of the fluorescence intensity by factors of from 3 to 5 is shown experimentally. [ABSTRACT FROM AUTHOR]

We developed a six-axis multi-anvil press, ATSUHIME, for high-pressure and high-temperature in situ time-of-flight neutron powder diffraction experiments. The press has six orthogonally oriented hydraulic rams that operate individually to compress a cubic sample assembly. Experiments indicate that the press can generate pressures up to 9.3 GPa and temperatures up to 2000 K using a 6-6-type cell assembly, with available sample volume of about 50 mm³ . Using a 6-8-type cell assembly, the available conditions expand to 16 GPa and 1273 K. Because the six-axis press has no guide blocks, there is sufficient space around the sample to use the aperture for diffraction and place an incident slit, radial collimators, and a neutron imaging camera close to the sample. Combination of the six-axis press and the collimation devices realized high-quality diffraction pattern with no contamination from the heater or the sample container surrounding the sample. This press constitutes a new tool for using neutron diffraction to study the structures of crystals and liquids under high pressures and temperatures. [ABSTRACT FROM AUTHOR]

We have developed a room temperature fabrication technique for hybrid bulk heterojunction solar cells based on silicon nanocrystals (Si-ncs) embedded in polythieno[3,4-b]thiophenebenzodithiophene (PTB7) and that exhibit a high open-circuit voltage exceeding 1 V. This type of device outperforms the open-circuit voltage of analogous devices based on Si-ncs within poly(hexylthiophene) (P3HT). We also demonstrate that three dimensional surface engineering of Si-ncs by microplasma processing in ethanol can be used to enhance the electronic interactions with PTB7, without using any surfactant, and increasing the power conversion efficiency. [ABSTRACT FROM AUTHOR]

We report on an atmospheric-pressure dc microplasma that can be used to passivate silicon nanocrystals (SiNCs) in ethanol and that stabilizes their optoelectronic properties. We show that microplasma processing enhances the SiNCs photoluminescence intensity by factor of more than ten times and ∼80 nm redshift of its maximum. The microplasma induces the replacement of hydrogen terminations with hydroxyl-/organic-based bonds. The resulting surface characteristics are responsible for the formation of conductive and stable SiNCs self-organized assemblies extending over 0.5 mm after dewetting on a substrate. [ABSTRACT FROM AUTHOR]

Light trapping is of importance in thin-film silicon solar cells for achieving a higher photocurrent. In this letter, we propose a unique cell structure incorporating submicron-sized light scatterers to enhance light trapping in the near-infrared (NIR) region. The effect of NIR light trapping is demonstrated in substrate-type hydrogenated amorphous/microcrystalline silicon tandem solar cells. By introducing the light scatterers at the interface between the top and bottom subcells, the NIR response of the solar cell is improved, where Mie scattering plays an essential role in increasing the optical path length of the NIR light. [ABSTRACT FROM AUTHOR]

The gas phase kinetics in a high-pressure hydrogen diluted silane plasma has been studied at time scales of 10-2–6×102 s. The time-resolved gas phase composition shows the following kinetics at different time scales: silane decomposition and polysilane generation in <=2×10-1 s, nanoparticle formation and plasma density reduction in 10-1–100 s, polysilane accumulation in 100–102 s, and silane depletion and electrode heating in >=101 s. Disilane radicals are implied to be the dominant film precursors in addition to silyl radicals. [ABSTRACT FROM AUTHOR]

Mass spectra of positive ions (cations) and neutrals have been measured in hydrogen diluted silane plasmas at gas pressures of 0.1–10 Torr. The mass spectrum of ions changes with the pressure, while that of neutrals maintains a similar shape. The dominant ion species varies from a hydrogen ion group at <=0.5 Torr to a monosilicon hydride ion group at ≈0.5–1 Torr and polysilicon hydride ion groups at >=1 Torr, which is determined from ionization channels and consecutive ion-molecule reactions. The ion bombardment is suppressed with the pressure, from several tens of eV at <=1 Torr to a few eV at >=7 Torr. [ABSTRACT FROM AUTHOR]

It is demonstrated that the signature of bulk hydrogen stretching modes in the infrared of microcrystalline silicon (μc-Si:H) deposited at high deposition rates can be used for solar cell optimization in the high pressure depletion regime. A relation between the performance of a p-i-n solar cell and the hydride stretching modes corresponding to hydrogenated crystalline grain boundaries is observed. These crystalline surfaces show postdeposition oxidation and the absence of these surfaces in the μc-Si:H matrix reflects device grade microcrystalline material. [ABSTRACT FROM AUTHOR]

Optical and electric properties in Zr-doped In2O3 epitaxial layers were systematically investigated. The films at Zr concentrations of 0.3–0.5 at. % are found to be superior transparent conductive oxides in transparency in near infrared wavelength region and Hall mobility compared to Sn-doped In2O3. Maximum mobilities are over 100 cm2/V s and corresponding carrier densities are approximately 1×1020 cm-3. From the relationship between the values of Hall mobility and carrier concentration of the epilayers, a number and/or effects of multicharged and neutral scattering centers of electrons seem to be reduced. [ABSTRACT FROM AUTHOR]

Optical and electric properties in Zr-doped In2O3 epitaxial layers were systematically investigated. The films at Zr concentrations of 0.3–0.5 at. % are found to be superior transparent conductive oxides in transparency in near infrared wavelength region and Hall mobility compared to Sn-doped In2O3. Maximum mobilities are over 100 cm2/V s and corresponding carrier densities are approximately 1×1020 cm-3. From the relationship between the values of Hall mobility and carrier concentration of the epilayers, a number and/or effects of multicharged and neutral scattering centers of electrons seem to be reduced. [ABSTRACT FROM AUTHOR]

We have fabricated high-performance p–n+ heterojunctions of homoepitaxial diamond (B-doped film: p type) and hydrogenated amorphous silicon (P-doped a-Si:H film: n type). Current–voltage (I–V) characteristics of the p–n+ heterojunctions at room temperature show excellent rectification properties with an ideality factor n of 1.23 and undetectable leakage current at reverse bias condition. Capacitance–voltage (C–V) characteristics show a large difference of space-charge densities (net acceptor densities) in the bulk and near-surface (interface) regions of the diamond films and a strong frequency dependence in the forward-bias region. The former result indicates that the hydrogen passivation of boron in diamond during the a-Si:H deposition occurs in the near-surface region which gives rise to a reduction of the acceptor density in the depletion region. The latter result indicates an increment of hydrogen-related defect states in the near-surface region of the diamond film. An idealized energy-band diagram for the p–n+ heterojunctions has been constructed on the basis of the negative-electron-affinity model. [ABSTRACT FROM AUTHOR]

{100} oriented Pb(Zr,Ti)O[sub 3] (PZT) thin films were deposited by metalorganic chemical vapor deposition on both Ir/MgO(100) and Ir/MgAl[sub 2]O[sub 4]/SiO[sub 2]/Si(100) substrates. The x-ray [uppercase_phi_synonym]-scan spectra for the (202) reflections revealed each film had fourfold symmetry, which was epitaxially grown as cube-on-cube. The switchable polarization (Q[sub sw]) of the PZT capacitor on the MgO substrate attained 100 μC/cm[sup 2] at 1.8 V; however, PZT capacitors on Si had a Q[sub sw] of 23 μC/cm[sup 2]. This difference in Q[sub sw] is attributed to the volume fraction of (001) orientation of each PZT film. The difference in orientation between the two kinds of PZT films does not seem to depend on misfit of lattice parameters between PZT and Ir, but on the stress caused by the difference in the thermal expansion coefficients of MgO and Si. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Low-temperature processing for high-performance solar cells based on hydrogenated microcrystalline silicon (μc-Si:H) has been developed using a conventional rf plasma-enhanced chemical vapor deposition (PECVD) technique at an excitation frequency of 13.56 MHz under a high deposition pressure condition. Among pin type solar cells, it is found that deposition temperature of i-layer at 140 °C is effective particularly for improving open circuit voltage (Voc), surprisingly without deteriorating short circuit current or fill factor. Carrier density of undoped μc-Si abruptly decreases for deposition temperatures lower than 180 °C, and the improvement of Voc is ascribed to a decrease of shunt leakage current arising from the oxygen-related donors. This implies that oxygen-related donors can be passivated at low deposition temperatures and that hydrogen plays an important role for the passivation. We propose a simple model for the hydrogen passivation of oxygen related donors. We apply this passivation technique to solar cells, and consequently a conversion efficiency of 8.9% (Voc=0.51 V, Jsc=25 mA/cm[sup -1], FF=0.70) has been obtained in spite of an oxygen concentration of 2x10[sup 19] cm[sup -3] in combination with device optimization such as a p-layer. Effect of deposition temperature of i-layer upon other solar cell parameter, short circuit current, and fill factor is also discussed. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Fe-doped semi-insulating In1-x Gax Asy P1-y (0≤y≤1, y=2.2x) epitaxial layers lattice matched to InP with nearly intrinsic carrier concentrations have been successfully grown over the entire composition range by liquid phase epitaxy. Maximum resistivities as high as 8×107 Ω cm for InP, 2×105 Ω cm for InGaAsP (y=0.57), and 2×103 Ω cm for InGaAs (y=1) have been achieved. The critical growth temperature necessary to obtain semi-insulating layers significantly decreased as the composition was varied from y=0 to y=1. The Fe doping characteristics are well defined by the composition dependence of the Fe distribution coefficient. [ABSTRACT FROM AUTHOR]

The structure of In1-xGaxAsyP1-y/InP superlattices (x=0.27 and y=0.60) is investigated by small-angle x-ray diffraction method. The interference peaks due to the superlattice structure were clearly observed up to the 6th order. The period of the superlattice was determined from the angular positions of the peaks using the modified Bragg’s law. By analyzing the diffraction patterns of the first and the secondary peaks according to the optical multilayer theory, the thickness of each component (In1-xGaxAsyP1-y and InP) was uniquely determined within an error of ±1 Å. This method can be used to determine any type of superlattice structure. [ABSTRACT FROM AUTHOR]

The interface disorder in quantum wells (QW’s) grown by molecular beam epitaxy on 0.5°-misoriented (111)B GaAs substrates was characterized by low-temperature photoluminescence and by transmission electron microscopy. It was found that the abruptness of the heterointerface of (111)B QW’s is as sharp as that of (100) QW’s. The effect of growth interruption at a high substrate temperature of 720 °C on the interface disorder was also studied and was found to be detrimental. [ABSTRACT FROM AUTHOR]

The Fe acceptor level in In1-xGaxAsyP1-y lattice matched to InP (x=0.47y) is investigated employing current-voltage characteristics and deep level transient spectroscopy. The activation energy decreases as the proportion of arsenic, y, increases. However, considering the band-edge discontinuity in this material, it was found that the Fe acceptor level is aligned at a constant energy. This is in excellent agreement with the vacuum referred binding energy model. [ABSTRACT FROM AUTHOR]

The activation ratio of Fe atoms introduced in semi-insulating (SI) InP layers grown by liquid phase epitaxy (LPE) and metalorganic chemical vapor deposition (MOCVD) has been investigated, employing the current-voltage characteristics of n+-SI-n+ InP diodes and secondary ion mass spectroscopy analysis. The result indicates that most Fe atoms in LPE-grown SI layers are electrically active as deep acceptors; however, a large amount of unactivated Fe atoms are present in MOCVD-grown SI layers. This difference between the two kinds of Fe-doped SI layers can be attributed to the difference in the growth mechanisms of LPE and MOCVD. [ABSTRACT FROM AUTHOR]

The effect of group V/III flux ratio γ on deep electron traps in AlxGa1-xAs (x=0.7) grown by molecular beam epitaxy at 720 °C has been studied by deep level transient spectroscopy. The photoluminescence characteristics of a GaAs single quantum well sandwiched by Al0.7Ga0.3As are determined by the electron traps denoted as E4–E6(E6’) in Al0.7Ga0.3As with the activation energies of 0.77 eV (E4), 0.72 eV (E5), 0.90 eV (E6), and 1.00 eV (E6’). The concentrations of these traps are minimized to the order of 1013 cm-3 at γ∼2 in spite of high Al content. [ABSTRACT FROM AUTHOR]

Investigates the role of hydrogen in hydrogenated microcrystalline silicon films (muc-Si:H) formation using hydrogen plasma treatments. Induction of a-Si:H layer by hydrogen plasma conditions; Observation of the Raman spectra in a-Si:H films; Implications for determining the cause of atomic hydrogen-induced subsurface reaction.

We have developed hydrogenated microcrystalline silicon germanium, which exhibits a red-shifted absorption spectrum relative to hydrogenated microcrystalline silicon, as a candidate material for the bottom cell of amorphous silicon-based tandem solar cells. Optical absorption, x-ray diffraction, and Raman scattering spectra are presented in addition to optoelectronic properties and light-induced changes. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Details the fabrication of a gallium indium phosphide/aluminum gallium indium phosphide visible laser with a real-index guide structure by one-step metalorganic vapor phase epitaxy. Use of simultaneous impurity doping; Achievement of self-aligned current-confinement structure.

Photoinduced structural change in hydrogenated amorphous silicon (a-Si:H) has been studied by a sensitive bending detection method using an optical lever. We observed that a-Si:H films show not only thermal expansion due to a photothermal effect but also residual and persistent expansion after light soaking. The volume change is recovered by thermal annealing at 200 °C. A dehydrogenated sample annealed at 550 °C and a microcrystalline sample, in which photoinduced defects are not created, show little photoinduced expansion. The photoinduced expansion and photoinduced defect density show identical time evolution. These results suggest that the photoinduced expansion is related to the photoinduced defect creation. A quantitative evaluation of the photoinduced expansion indicates that the photoinduced structural change is spread over several molecular volumes around a photocreated defect. © 1998 American Institute of Physics. [ABSTRACT FROM AUTHOR]