bluuebunny/crossref_metadata_2025_split huggingface dataset:
Quantum Confinement in Single Layer a-Si:H Films
Authors: Koehler S. A. , Fritzsche H. 
Published: April 2011

AbstractQuantum confinement effects in the transmission spectrum of thin amorphous silicon, a-Si:H, films require a coherence length comparable to the film thickness, as well as good film homogeneity. After a careful investigation, we conclude that there is no quantum confinement in single layer a-Si:H films at room temperature.
Improvement of the ITO-P Interface in a-Si:H Solar Cells Using a Thin SiO Intermediate Layer
Authors: Nunes de carvalho C. , De Nijs J. M. M. , Ferreira I. , Fortunato E. , Martins R. 
Published: April 2011

AbstractThe use of ITO thin films on glass/ITO/p-i-n/metal amorphous silicon solar cells is reviewed. It is suggested a new application for silicon monoxide thin films on the ITO-p interface, as an intermediate layer, to minimize the ITO thin film deterioration process, during the early stage of exposure to a silane plasma rich in hydrogen. The thickness of the silicon monoxide thin films is chosen not to worsen the optical and electrical properties of the ITO thin films. The ITO-p interface is optimized (due to impurities diffusion decrease), leading to an overall improvement of the device performance
Nano-Scale Resolved Detection of Photo-Current in a-Si:H Films
Authors: Koida Takashi , Kawasaki Masashi , Maruyama Ryuichiro , Matsuse Mitsutaka , Koinuma Hideomi 
Published: April 2011

AbstractThe growth mode of a-Si:H plasma CVD film was observed by AFM to range from homogeneous deposition to heterogeneous island formation depending on the substrate material and deposition temperature. The correlation between the grain-like structure and electric property of the film deposited on transparent conductive SnO2, substrates has been elucidated by using an AFM with a conductive cantilever. The local distribution of photo-current in the a-Si:H films was found to agree well with the topographic image; the photo-current around the grain boundaries was lower than that on the grains. The effect of surface treatment with an aqueous HF solution indicates that the imhomogeneity in the photo-current originates from the preferential oxidation around the grain boundaries rather than intrinsic electric property.
A Novel Device Structure for High Voltage, High Performance Amorphous Silicon Thin-Film Transistors
Authors: Miri A. M. , Gudem P. S. , Chamberlain S. G. , Nathan A. 
Published: April 2011

AbstractConventional high voltage thin-film transistors (HVTFTs) suffer from performance limitations such as low on-current, Vx. shift and large curvature in the linear region of the output characteristics. These limitations are associated with the highly resistive dead region in conventional HVTFT structures. In this paper, we present a novel TFT structure which has a high on-current, improved output characteristics in the linear region, and no Vx, shift. The higher on-current and significant improvement in output characteristics allows faster switching. Elimination of the Vx shift leads to more reliable circuit operation. The new structure is based on the conventional low voltage TFT (LVTFT) structure except that it does not suffer from low-voltage breakdown. The low-voltage breakdown of the gate nitride in conventional LVTFTs is perceived to be due to spiking of the drain metallization into the underlying layers which creates regions of very high electric field. In our novel structure, a higher breakdown is achieved by locating the metal contacts away from the gate edge while keeping the necessary drain to gate overlap through a heavily doped microcrystalline layer. Therefore, the new TFT extends the same performance as LVTFTs to high voltage operation. Furthermore, this structure also enhances the yield and reliability by minimizing the common faults in TFTs such as short circuits between gate, source and drain.
On the Investigation of Power and Reliability Performance of Pseudomorphic AlGaAs/InGaAs HEMT's
Authors: Li G.P. , Chou Y.C. , Chen Y.C. , Wu C.S. , Yu K.K. , Midford T.A. , Liu Y. , Sonek G.J. , Wei X. , Tromberg B.J. 
Published: April 2011

AbstractIn this work, power and reliability performance of pseudomorphic AIGaAs/InGaAs HEMT's are investigated by 2-D device simulation, spatially-resolved electro-luminescence, light emission spectra analysis, and gate current instabilities. A two-dimensional device simulation was used to exploit the off/on state breakdown origins in the power PHEMT's and to explore the physical mechanisms responsible for light emission in both conditions. A correlation between simulated results and light emission spectra highlights the breakdown origins in PHEMT's.PHEMT's subjected to off-state breakdown stress and on-state hot carrier stress show changes in device characteristics. While gate leakage current, i.e. a surface leakage component associated with the surface passivation layer is reduced by these stresses, a reduction in drain current, transconductance degradation, and an increase in the impact ionization generated gate current are also observed.Further improvement in off/on state breakdown voltages and device reliability calls for device structure optimization for lower electric field design, surface passivation treatment for lower surface leakage current, and Schottky barrier enhancement for lower gate current.
Selective-Area Epitaxy and In-Situ Etching of Gaas Using Tris- Dimethylaminoarsenic By Chemical Beam Epitaxy
Authors: Li N. Y. , Tu C. W. 
Published: April 2011

AbstractIn this study, we shall first report selective-area epitaxy (SAE) of GaAs by chemical beam epitaxy (CBE) using tris-dimethylaminoarsenic (TDMAAs), a safer alternative source to arsine (AsH3), as the group V source. With triethylgallium (TEGa) and TDMAAs, true selectivity of GaAs can be achieved at a growth temperature of 470°C, which is much lower than the 600°C in the case of using TEGa and arsenic (As4) or AsH3. Secondly, we apply SAE of carbon-doped AIGaAs/GaAs to a heterojunction bipolar transistor (HBT) with a regrown external base, which exhibits a better device performance. Finally, the etching effect and the etched/regrown interface of GaAs using TDMAAs will be discussed.
Cleaved Facets in Gan by Wafer Fusion of Gan to Inp
Authors: Sink R. K. , Keller S. , Keller B. P. , Babić D. I. , HOLMES A. L. , Kapolnek D. , Wu X. H. , Speck J. S. , Denbaars S. P. , Bowers J. E. 
Published: April 2011

AbstractBasal plane sapphire is a common substrate for the heteroepitaxy of GaN. This presents a challenge for fabrication of cleaved facet GaN lasers because the natural cleavage planes in (0001) α-A12O3 are not perpendicular to the wafer surface. This paper describes a method for achieving perpendicular cleaved facets through wafer fusion that can potentially be used to fabricate GaN based in-plane lasers. We demonstrate successful fusion of GaN to InP without voids or oxide at the interface and fabricate optically flat cleaved GaN facets that are parallel to the crystallographic planes of the host InP. I-V measurements have been performed across the n-N fused interface. These results show that the fused interface exhibits a barrier for electrons passing from the InP to the GaN and ohmic conduction of electrons moving in the opposite direction.
Interactions at Metaijinp Interfaces Formed at 300K and 77K
Authors: Palmer J.W. , Anderson W.A. , Hoelzer D.T. , Hardtdegen H. 
Published: April 2011

AbstractDepositing Pd or Au on n-InP at cryogenic substrate temperatures has previously been found to significantly increase the barrier height of the resulting Schottky diode. Cross-sectional transmission electron microscopy (XTEM) has been performed on Pd/InP and Au/InP interfaces formed at room temperature (RT) and low temperature (LT) to determine the differences responsible for the change in barrier height. In the Pd case, a solid state amorphization which occurs at the interface upon RT metal deposition is nearly eliminated in as-deposited LT Pd/InP diodes. In the Au case, RT deposition results in the initial monolayers of Au entering the InP lattice, while no such effect was observed in the LT Au/InP diodes. It is clear that the LT deposition dramatically reduces the interaction between the metal and substrate, resulting in a greater barrier height. Enhanced barrier height Schottky diodes are crucial to the development of optical and electronic devices on InP. Preliminary results will be discussed on metalsemiconductor- metal (MSM) photodetectors and metal-semiconductor field-effect-transistors (MESFET's) fabricated using the LT process.
A Study of Annealing Behavior of EL2 and EL6 Groups in SI-GaAs
Authors: Fengmei Wu , Zhouying Zhao 
Published: April 2011

AbstractWe present annealing behavior for EL2 and EL6 groups as dominant deep levels in semiinsulating GaAs using Photo Induced Transient Spectroscopy (PITS) measurement. During rapid thermal annealing, a relation has been identified between EL2 group at 0.79 and 0.82 eV and EL6 group at 0.24, 0.27 and 0.82 eV below the conduction band. It is found that they may be close in structure, and belong to the EL2 and EL6 groups, respectively. In rapidly annealed samples, the quantity of all defects in the EL2 group increases, while that in the EL6 group decreases. However, by furnace annealing at 950°C for 5 hours, some of the defects in the EL2 group break up, and the quantity of all defects in the EL6 group increases. It is suggested that the EL2 group and EL6 group are related in their microscopy structures. We then discuss a relation between the two groups and their origins.
The Electric Field Measuring by Phase Selective Photoreflectance
Authors: Hwang J. S. , Chou W. Y. , Tyan S. L. , Wang Y. C. , Shen H. 
Published: April 2011

AbstractThe built-in electric fields in a MBE grown δ-doped GaAs homojunction have been investigated by the techniques of photoreflectance and phase suppression. Two Franz-Keldysh oscillation features originating from two different fields in the structure superimpose with each other in the photoreflectance spectrum. By properly selecting the reference phase of the lock-in amplifier, one of the features can be suppressed, thus enabling us to determine the electric fields from two different regions. We have demonstrated that only two PR spectra, in-phase and outphase components, are needed to find the phase angle which suppresses one of the features. The electric field in the top layer is 3.5 ± 0.2 × 105 V/cm, which is in good agreement with theoretical calculation. The electric field in the buffer layer is 1.2 ± 0.1 × 104 V/cm, which suggests the existence of interface states at the buffer/substrate interface.
Passivation of Carbon Doping in InGaAs During ECR-CVD of SiNx
Authors: Ren F. , Hamm R. A. , Wilson R. G. , Pearton S. J. , Lothian J. R. 
Published: April 2011

AbstractInGaAs (C) grown by gas-source MBE is found to contain significant concentrations 5 × 1018 cm−3 of hydrogen that is incorporated from the source gases. Subsequent deposition of ECR-CVD SiNx films as surface encapsulation produces additional hydrogen incorporation from the SiD4/N2 precursors, but actually reactivates C acceptors that were passivated in the asgrown InGaAs. Further thermal treatments produce substantial hydrogen in-diffusion from the SiNx film into the InGaAs, causing changes in sheet resistance and contact resistance. These processes simulate several steps in the formation of the base mesa of an InGaAs-based heterojunction bipolar transistor, and show how subtle changes in the temperature of these processes can affect subsequently device performance and apparent reliability.
Polarization Control of Vertical-Cavity Surfaceemitting Lasers by Tilted-Etching of Cavity
Authors: Chu Hye Yong , Yoo Byueng-Su , Park Min Soo , Park Hyo-Hoon 
Published: April 2011

AbstractWe performed a polarization control method for vertical-cavity surface-emitting lasers by tilted-etching of the air-post. Circular laser posts were etched by tilting the substrate toward [110] or [110] direction with an angle of 15° ˜ 20° using reactive ion beam etching. For the laser devices with a diameter of 7 ˜ 10 μm, we observed outstanding selectivity of the polarization state. We found a dominant polarization perpendicular to the tilted direction. The maximum orthogonal polarization suppression ratio was about 25 dB. The selectivity of polarization in the tilted laser post devices is interpreted to be originated from the difference of optical losses of the two waves polarized to the [110] and [110] directions.
Properties of H, O and C in GaN
Authors: Pearton S. J. , Abernathy C. R. , Lee J. W. , Vartuli C. B. , MacKenzie J. D. , Ren F. , Wilson R. G. , Zavada J. M. , Shul R. J. , Zolper J. C. 
Published: April 2011

AbstractThe electrical properties of the light ion impurities H, O and C in GaN have been examined in both as-grown and implanted material. H is found to efficiently passivate acceptors such as Mg, Ca and C. Reactivation occurs at ≥450°C and is enhanced by minority carrier injection. The hydrogen does not leave the GaN crystal until >800°C, and its diffusivity is relatively high (˜10−11cm2/s) even at low temperatures (<200°C) during injection by wet etching, boiling in water or plasma exposure. Oxygen shows a low donor activation efficiency when implanted into GaN, with an ionization level of 30 - 40 meV. It is essentially immobile up to 1100°C. Carbon can produce low p-type levels (3×1017cm−3) in GaN during MOMBE, although there is some evidence it may also create n-type conduction in other nitrides.
Long Wavelength Shifting and Broadening of Quantum Well Infrared Photodetector Response Via Rapid Thermal Annealing
Authors: Sengupta D.K. , Fang W. , Malin J.I. , Kuo H.C. , Horton T. , Curtis A. , Gardner N.F. , Flachsbart B. , Wohlmuth W. , Turnbull D. , Chuang S.L. , Hsieh K. C. , Cheng K.Y. , Adesida I. , Feng M. , Bishop S.G. , Stillman G. E. 
Published: April 2011

AbstractA shift in the peak response wavelength and a broadening of the photoresponse spectrum is demonstrated for intersubband absorption in n-doped GaAs/AIGaAs multiple quantum well detectors following intermixing of the well and barrier layers during rapid thermal annealing. In general, a decrease in performance is observed for the RTA QWIPs when compared to the as-grown detectors. The peak absolute response of the annealed QWIPs is lower by almost a factor of four, which results in corresponding decrease in quantum efficiency. In addition, the noise performance results in a detectivity which is five times lower than that of QWIPs fabricated from as-grown structures.
Temperature Dependence of the Optical Absorption Edge in Indium Phosphide
Authors: Beaudoin M. , Johnson S.R. , Devries A.J.G. , Mohades-Kassai A. , Tiedje T. 
Published: April 2011

AbstractOptical bandgap thermometry is a new method for measuring the temperature of semiconductor substrates. In this method, the temperature of the substrate is inferred from the wavelength of the onset of transparency of the substrate which is a measure of its bandgap. Common configurations of this technique are diffuse reflectance and transmittance. In order to calibrate these spectra to substrate temperature and to better understand the temperature dependence of the absorption edge, the transmittance spectra of semi-insulating InP:Fe and n-type InP:S substrates have been measured as a function of temperature in a tube. The width of the absorption edge (Urbach parameter) is found to increase linearly with temperature from 8.7 meV at room temperature to 15.7 meV at 595°C for semi-insulating InP:Fe while it remains independent of temperature at a value of about 21.5 meV for heavily doped (6.5×1018 cm−3) InP:S. For InP:Fe, the temperature dependent part of the width is smaller than predicted by the standard theory where the width of the edge is proportional to the phonon population. The values of the Urbach parameter for InP:Fe are higher than those of semi-insulating GaAs which is attributed to the higher ionicity of InP.
Tem Structural Characterization of Nm-Scale Islands in Highly Mismatched Systems
Authors: Ruvimov S. , Liliental-Weber Z. , Ledentsov N.N. , Grundmann M. , Bimberg D. , Ustinov V.M. , Egorov A.YU. , Kop'ev P.S. , Alferov Zh.I. , Scheerschmidt K. , Gösele U. 
Published: April 2011

AbstractTransmission electron microscopy has been applied to study the ordering in size and shape of InAs quantum dots and in their lateral distribution. InAs islands were grown by MBE on GaAs substrates at different As-pressures and growth temperatures. Experiments with growth interupption support the theoretical predictions concerning equilibrium island size, shape and arrangement. The stability of the equilibrium dot arrays to changing of growth conditions was studied by varying the deposition temperature, arsenic pressure or growth interruption time. Significant deviation from the optimal As-pressure towards both the lower and higher values was shown to supress the formation of InAs dots resulting either in mesoscopic InAs clusters or 2D corrugated islands. Energy benefit due to the strain relaxation at island edges explains the experimental results better than kinetic consideration.
Theoretical Study of InAsSb/InTlSB Superlattice for the Far Infrared Detector
Authors: Iyer S. , Chowdhury-Nagle S. , Li J. , Bajaj K.K. 
Published: April 2011

AbstractWe propose a novel superlattice (SL) InAsySb1−y)/InxTl1−xSb lattice matched to InSb for a potential application as an infrared detector material in the 8–12 μm wavelength range. We report on the results of energy band calculations for this SL using the modified Kronig-Penney model. Our preliminary calculations indicate that InAs0.07Sb0.93/In0.93Tl0.07Sb would exhibit a type-I SL with conduction band offset of 34 meV and valence band offset of 53 meV at 0K. Due to the lack of accurate information on material parameters, namely, energy offsets and effective masses of InTlSb, these were estimated by comparison with the behavior of HgCdTe system. The theory predicts three heavy hole subbands and one partially confined electron in the 30Å InAs0.07Sb0.93/100Å In0.93Tl0.07Sb SL. The band gap of the SL was computed to be 0.127 eV (9.7 μm). It is expected that this SL will allow improvements in the InTlSb epilayers’ structural quality as it will be sandwiched between higher quality zincblende InAsSb layers.
Surface Passivation of Gaas-Based Phemt by Hydrogen Ion Irradiation
Authors: Shi Song S. , Chang Ying-Lan , Hu Evelyn L. , Brown Julia J. 
Published: April 2011

AbstractSurface passivation is a key issue in compound semiconductor device technology. The high density of surface states on unpassivated surfaces can lead to excessive non-radiative recombination at the surface, affecting optical devices, or provide leakage and low-field breakdown in electronic devices. Our previous studies on low energy, low-dose hydrogen ion treatment carried out at room temperature showed long-term improvement in the optical properties of near surface quantum wells. We have accordingly applied this process to GaAs-based pseudomorphic HEMTs (PHEMT) in order to improve their power performance. Although our process is designed so that the hydrogen reactions are confined to the surface of the substrate, a critical factor in the success of this treatment is the extent of in-diffusion of the hydrogen, and the possibility of dopant passivation. PHEMT structures were hydrogenated at various conditions and both Hall mobility and carrier density were monitored. For a low hydrogen ion dose (3 × 1016 cm−2) at 80 eV energy, some degradation of Hall mobility and carrier density was noted after the treatment, but full recovery of both parameters was achieved after a 400°C thermal anneal. Much higher hydrogen doses resulted in severe degradation of mobility and carrier density, which were only partially recovered after thermal anneal. Measurements on actual PHEMT devices showed an approximately 15% decrease in the transconductance, and in addition, a 60% decrease in the gate-to-drain leakage current after irradiation with 80 eV hydrogen ions at a dose of 3 × 1016 cm−2. The decrease of the leakage current indicates that passivation is taking place. The decrease of the transconductance suggests that hydrogen may be diffusing into the regions of the dopants. Optimization of the hydrogenation parameters should allow leakage reduction without sacrifice of transconductance.
Surface Stabilization Of Inp Using Cds Thin Films
Authors: Davis A. , Dauplaise H.M. , Vaccaro K. , Demczyk B.G. , Ramseyer G.O. , Lorenzo J.P. 
Published: April 2011

AbstractA chemical bath deposition process was used to grow thin (25–200 Å) films of cadmium sulfide on (100) InP from an aqueous solution of ammonium hydroxide, cadmium sulfate, and thiourea at 75–85 °C. Reflection high energy electron diffraction (RHEED) and transmission electron microscopy (TEM) show that ˜30 Å films are amorphous, while thicker films exhibit a cubic polycrystalline microstructure, with a preferred orientation in the [110] direction. X-ray photoelectron spectroscopy (XPS) shows the CdS treatment both removes the native oxides of InP and forms a stabilizing layer which protects the substrate from re-oxidation. Quasistatic capacitance-voltage response of MIS capacitors on InP, with a CdS layer between the insulator and substrate, exhibits well defined regions of accumulation, depletion, and inversion, indicating a high-quality interface region. An experimental Cmin/Cox, value of 0.28 was obtained, compared to the theoretical value of 0.07. The density of interface states (Dit) was reduced from 1012 to 1011 eV−1cm−2 after CdS treatment when calculated by the high-low method. InP MISFETs fabricated using CdS interlayers showed greatly enhanced device performance over untreated MISFETs.
Luminescence Quenching in Erbium-Doped Hydrogenated Amorphous Silicon
Authors: Polman A. , Shin Jung H. , Serna R. , Hovenb G. N. Van Den , van Sark W. G. J. H. M. , Vredenberg A. M. , Lombardo S. , Campisano S. U. 
Published: April 2011

AbstractHydrogenated amorphous silicon thin films, co-doped with oxygen, are made using lowpressure chemical vapor deposition (LPCVD) or plasma-enhanced chemical vapor deposition (PECVD). The films are implanted with Er to a peak concentration of 0.2 at.%. Roomtemperature photoluminescence at 1.54 μm is observed in both amorphous materials, after thermal annealing at 300–400 °C. The PECVD films with low 0 content (0.3, 1.3 at.%) show a luminescence intensity quenching by a factor 7–15 as the temperature is raised from 10 K to room temperature. The quenching is well correlated with a decrease in luminescence lifetime, indicating that non-radiative decay of excited Er3+ is the dominant quenching mechanism as the temperature is increased. In the LPCVD films, with 31 at.% 0, the quenching is only a factor 3, and no lifetime quenching is observed. The results are interpreted in the context of an impurity Auger excitation model, taking into account the fact that oxygen modifies the Si bandgap and the Er-related defect levels in the gap.