bluuebunny/crossref_metadata_2025_split huggingface dataset:
A New Methodology For Designing Floating Ring Termination Technique In High Voltage Structure
Authors: Stefanov E. , Charitat G. , Bailon L. , Barbolla J. 
Published: April 2011

AbstractA new methodology to optimise the design of Floating Ring (FR) termination technique for high voltage device is presented. The basic idea is to simulate the blocking capability of the structure with only one guard ring and then extend the results to a multiple FR system. A second advantage of our method is to include the ring width in the optimisation process. The effectiveness and efficiency of our methodology is illustrated by optimising a FR structure with a junction depth xj=5 μm and Si substrate doping 2.1014cm−3 A seven rings structure is optimized giving 90 % efficiency in respect to the ideal plane parallel junction breakdown voltage VBD =840 V. Moreover the 2D simulation program POWER2D has been extended by an efficient numerical algorithm to reduce drastically the number of iterations when adjusting the quasi-Fermi potential of the rings.
Morphology Of Silicon Oxides On Silicon Carbide
Authors: O‘Brien M. L. , Pejdo S. , Nemanich R. J. 
Published: April 2011

AbstractThe development of high power devices based on silicon carbide requires a more complete understanding of the oxide formation process and interface characteristics. By using an integrated UHV system, samples were cleaned and oxides deposited in situ. The approach of the oxide formation process was to form the initial insulator, a few angstroms thick, and then deposit an oxide. Various deposition techniques are used in the oxide growth process; both thermal and plasma enhanced chemical vapor deposition were employed with two different precursors (oxygen and nitrous oxide), and the results were compared with thermal oxidation. The morphology of each of the deposited oxides was compared to the bare substrate and the thermal oxide wafers. This study focuses on the morphology of the different deposition processes using AFM. Examination of the morphology of the initial insulator growth process and the oxide deposition process gives insight into the physical characteristics of the silicon dioxide deposited on silicon carbide. The RMS values of the initial insulator formation and the control wafers are 0.93 and 0.95 nm respectively. Meanwhile, the RMS values for PECVD (200–400°C) and thermal CVD (400–600°C for oxygen-silane and 800–1000°C for nitrous oxide-silane) range from 1.43 to 1.93 nm.
Thin Film Diamond Field Effect Transistors For High Power Applications
Authors: Looi Hui Jin , Pang Lisa Ys , Jackman Richard B. 
Published: April 2011

AbstractEarly predictions that diamond would be a suitable material for high performance, high power devices were not supported by the characteristics of diodes and field effect transistors (FETs) fabricated on boron doped (p-type) thin film material. In this paper commercially accessible polycrystalline thin film diamond has been turned p-type by the incorporation of near surface hydrogen. Schottky diodes and metal-semiconductor FETs (MESFETs) have been fabricated using this approach which display unprecedented performance levels; diodes with a rectification ratio > 106, leakage currents < l nA, no indication of reverse bias breakdown at 100V and an ideality factor of 1.1 have been made. Simple MESFET structures that are capable of withstanding VDS values of 100V with low leakage and current saturation (pinch-off) characteristics have also been fabricated. Predictions based upon experiments performed on these devices suggest that optimised device structures will be capable of operation at power levels up to 20 W/mm, implying that thin film diamond may after all be an interesting material for power applications.
Junction Field Effect Transistors For High-Temperature Or High-Power Electronics
Authors: Zolperw J. C. 
Published: April 2011

AbstractJunction field effect transistors (JFETs) are attractive for high-temperature or highpower operation since they rely on a buried semiconductor junction, and not a metal semiconductor interface as in a metal semiconductor (MESFET) or heterojunction field effect transistor (HFET), for modulating the transistor channel. This is important since a metal/semiconductor interface often degrades at elevated temperatures, either due to the ambient temperature or to Joule heating at high current levels, while a buried semiconductor junction can withstand higher temperatures. In fact, for proper design, the JFET becomes limited by thermal carrier generation in the semiconductor and not metallurgical degradation of the gate electrode.In this talk an overview is given of JFET technology based on GaAs, SiC, and GaN. While impressive room temperature, high-frequency, results have been reported for GaAs JFET's with unit current gain cut-off frequencies up to 50 GHz, more work is needed to limit substrate conduction for optimum operation at 300 °C and above. For SiC JFETs, well behaved transistor operation has been maintained up to 600 °C, however, increased frequency performance is needed. More recently, a GaN JFET has also been demonstrated that is promising for similarly high temperature operation but is presently limited by buffer conduction. Future directions for each of these technologies, and potential extension to high power switching devices such as thyristors, will be presented at the conference.
A Thin-Film Silicon Solar Cell: Design and Processing Approach
Authors: Sopori Bhushan L. , Chen Wei , Madjdpour Jamal , Symko Marta 
Published: April 2011

AbstractWe present a new device structure for a high efficiency, thin-film, silicon solar cell. A preliminary design and an approach for fabrication of such a cell are discussed. The cell structure uses interface texturing and a back surface reflector for effective light trapping. A theoretical analysis is applied to determine the major parameters of the cell. These analyses indicate that a cell efficiency of about 18% is attainable with a Si film thickness of 10–15 μm, and grain size of about 50 μm. A method for making a large-grain thin cell is proposed.
In-Situ Surface Composition Measurements of CuGaSe2 Thin Films
Authors: Fons P. , Yamada A. , Niki S. , Oyanagi H. 
Published: April 2011

AbstractTwo CuGaSe2 films were grown by molecular beam epitaxy onto GaAs (001) substrates with varying Cu/Ga flux ratios under Se overpressure conditions. Growth was interrupted at predetermined times and the surface composition was measured using Auger electron spectroscopy after which growth was continued. After growth, the film composition was analyzed using voltage dependent electron microprobe spectroscopy. Film structure and morphology were also analyzed using x-ray diffraction and atomic force microscopy. The film with a Cu/Ga ratio larger than unity showed evidence of surface segregation of a second Cu-rich phase with a Cu/Se composition ratio slightly greater than unity. A second CuGaSe2 film with a Cu/Ga ratio of less than unity showed no change in surface composition with time and was also consistent with bulk composition measurements. Diffraction measurements indicated a high concentration of twins as well as the presence of domains with mixed c and a axes in the Ga-rich film. The Cu-rich films by contrast were single domain and had a narrower mosaics. High sensitivity scans along the [001] reciprocal axis did not exhibit any new peaks not attributable to either the substrate or the CuGaSe2 thin film.
Piezoelectric Photoacoustic Spectra In CuGaSe2 Thin Films Grown by Molecular Beam Epitaxy
Authors: Yoshino Kenji , Maruoka Daisuke , Kawahara Masakazu , Fukuyama Atsuhiko , Maeda Kouji , Fons Paul J. , Niki Shigeru , Yamada Akimasa , Ikari Tetsuo 
Published: April 2011

AbstractThe piezoelectric photoacoustic (PPA) spectra for Cu-rich CuGaSe2 (CGS)/GaAs epitaxial layers were successfully observed between liquid nitrogen and room temperatures for the first time. Bandgap energy of CGS (A band) is estimated to be 1.72 eV at liquid nitrogen temperature. The activation energies of three possible intrinsic defect levels are estimated to be about 80, 130 and 190 meV.
Sulfur Diffusion In Polycrystalline Thin-Film CdTe Solar Cells
Authors: Aslan M. H. , Song W. , Tang J. , Mao D. , Collins R. T. , Levi D. H. , Ahrenkiel R. K. , Lindstrom S. C. , Johnson M. B. 
Published: April 2011

AbstractX-ray diffraction and photoluminescence measurements have been used to characterize the diffusion of S into CdTe during post growth annealing of CdTe solar cells. For anneals at 410°C in the presence of CdCl2, evidence that both a CdTe1 xSx phase and nearly-pure CdTe are present near the back contact is observed. The ternary phase becomes more prominent and the S concentration increases with depth reaching roughly 4–5% near the CdS interface. Much less diffusion is observed at 350°C while for a 460°C anneal, CdTe1-xSx with a S concentration near 5% is found throughout the layer. The presence of CdC12 during the anneal enhances the interdiffusion.
Interface Reactions in CdTe Solar Cell Processing
Authors: Albin D. , Dhere R. , Swartzlander-Guest A. , Rose D. , Li X. , Levi D. , Niles D. , Moutinho H. , Matson R. , Sheldon P. 
Published: April 2011

AbstractCurrently, the best performing CdS/CdTe solar cells use a superstrate structure in which CdTe is deposited on a heated CdS/SnO2/Glass substrate. In the close-spaced-sublimation (CSS) process, substrate temperatures in the range 550°C to 620°C are common. Understanding how these high processing temperatures impact reactions at the CdS/CdTe interface in addition to reactions between previously deposited layers is critical. At the SnO2/CdS interface we have determined that SnO2 can be susceptible to reduction, particularly in H2 ambients. Room-temperature sputtered SnO2 shows the most susceptibility. In contrast, higher growth temperature chemical vapor deposited (CVD) SnO2 appears to be much more stable. Elimination of unstable SnO2 layers, and the substitution of thermal treatments for H2 anneals has produced total-area solar conversion efficiencies of 13.6% using non-optimized SnO2 substrates and chemical-bath deposited (CBD) CdS. Alloying and interdiffusion at the CdS/CdTe interface was studied using a new lift-off approach which allows enhanced compositional and structural analysis at the interface. Small-grained CdS, grown by a low-temperature CBD process, results in more CdTe1-x.Sx alloying (x=12–13%) relative to larger-grained CdS grown by high-temperature CSS (x7sim;2–3%). Interdiffusion of S and Te at the interface, measured with lift-off samples, appears to be inversely proportional to the amount of oxygen used during the CSS CdTe deposition. Our highest efficiency to date using CSS-grown CdS is 10.7% and was accomplished by eliminating oxygen during the CdTe deposition.
Multijunction InGaAs Thermophotovoltaic Devices
Authors: Fatemi Navid S. , Wilt David M. , Jenkins Phillip P. , Weizer Victor G. , Murray Christopher S. 
Published: April 2011

AbstractA monolithic interconnected module (MIM) structure has been developed for thermophotovoltaic (TPV) applications. The MIM consists of many individual InGaAs cells series-connected on a single semi-insulating (S.I.) InP substrate. An infrared (IR) back surface reflector (BSR), placed on the rear surface of the substrate, returns the unused portion of the TPV radiator output spectrum back to the radiator for recuperation, thereby providing for high system efficiencies. MIMs were fabricated with an active area of 0.9×l cm, and with 15 cells monolithically connected in series. Both lattice-matched and lattice-mismatched InGaAs/InP devices were fabricated, with bandgaps of 0.74 and 0.55 eV, respectively. The 0.74 eV MIMs demonstrated an open-circuit voltage (Voc) of 6.16 V and a fill factor of 74.2% at a short-circuit current (Jsc) of 0.84 A/cm2, under flashlamp testing. The 0.55 eV MIMs demonstrated a Voc of 4.85 V and a fill factor of 57.87percnt; at a Jsc of 3.87 A/cm2 Electrical performance results for these MIMs are presented.
The Effect of The Zn Interstitial Defect on the Performance of p/n InP Solar Cells
Authors: Hoffman R. W. , Fatemi N. S. , Weizer V. G. , Jenkins P. , Stan M. A. , Ringel S. A. , Sieg R. M. , Scheiman D. A. , Wilt D. M. , Brinker D. J. 
Published: April 2011

AbstractThe bandgap of InP is near ideal for the high theoretical conversion efficiency of the air mass zero (AM0) light spectrum experienced in space. This combined with the well known radiation resistance makes InP an ideal candidate for space solar cell use. The p/n configuration has several advantages over the n/p configuration, however, the conversion efficiency of p/n InP cells has been low compared to the n/p configuration, mostly do to poor performance of the Zn doped emitter. We have recently achieved a 17.6% AMO conversion efficiency for a p/n InP cell on an InP substrate and have achieved this record efficiency through understanding of the role of Zn interstitial defects and the hydrogen interactions with these defects. The effect of the Zn defect on device performance will be described.
Spectral Utilization in Thermophotovoltaic Devices
Authors: Clevenger Marvin B. , Murray Christopher S. , Riley David R. 
Published: April 2011

AbstractMultilayer assemblies of epitaxially-grown, Ill-V semiconductor materials are being investigated for use in thermophotovoltaic (TPV) energy conversion applications. It has been observed that thick, highly-doped semiconductor layers within cell architectures dominate the parasitic free-carrier absorption (FCA) of devices at wavelengths above the bandgap of the semiconductor material. In this work, the wavelength-dependent, free-carrier absorption of p- and n-type InGaAs layers grown epitaxially onto semi-insulating InP substrates has been measured and related to the total absorption of long-wavelength photons in thermophotovoltaic devices. The optical responses of the TPV cells are then used in the calculation of spectral utilization factors and device efficiencies.
SiGe Thin-Film Structures for Solar Cells
Authors: Bremond G. , Daami A. , Laugier A. , Seifert W. , Kittler M. , Poortmans J. , Caymax M. , Said K. , Konuma M. , Gutjahr A. , Silier I. 
Published: April 2011

AbstractIn order to study their applicability as the active base material in Si thin crystalline film solar cell technology, SiGe relaxed layers grown by Liquid Phase Epitaxy (LPE) and Chemical Vapor Deposition (CVD) on Si substrates are investigated by optical and electrical measurements (TEM, EXD, PL, EBIC). The main results of this work is to point out the improvement of the SiGe active base layer by using smooth Ge graded SiGe buffer layer and remote plasma hydrogenation. TEM, EXD, PL experiments show the effect of the Ge graded buffer layer grown using LPE, by confining the threading dislocations in the SiGe buffer layer close to the Si/SiGe interface. EBIC measurements reveal low recombination activity of dislocations at 300 K providing the diffusion length exceeds the 15 μm layer thickness The enhanced luminescence of SiGe near bandgap indicates that remote plasma hydrogenation induces a decrease of the non-radiative recombination pathways due to dislocations on CVD layers where defect recombinations dominate as indicated by EBIC measurements.This study points out the importance of controlling relaxed SiGe layers with good minority carrier recombination quality as a key issue for the optimization of new SiGe/Si based solar cells.
Amorphous Silicon Based Waveguides And Light Modulators For Silicon Low-Cost Photonic Integrated Circuits
Authors: Cocorullo G. , Corte F. G. Della , Rosa R. De , Rendina I. , Rubino A. , Terzini E. 
Published: April 2011

AbstractThis paper reports about the fabrication and experimental test of an interferometric light intensity modulator integrated in a low loss (0.7 dB/cm), amorphous silicon based waveguide. It measures approximately 1 mm in length, while its cross section is 30-μm-wide and 3-μm-high. The device, which exploits the strong thermo-optic effect in thin film a-Si for its operation, is designed for application at the infrared wavelengths of 1.3 and 1.55 μm. The measured maximum operating on-off switching frequency of the device is 600 kHz. The very simple fabrication technology involves maximum process temperatures of 230 °C, and is therefore compatible with the standard microelectronic technology. This offers a new opportunity for the integration of optical and electronic functions on the same substrate.
Er-Doped Porous Silicon Led For Integrated Optoelectronics
Authors: Tsybeskov L. , Grom G. F. , Hirschman K. D. , Lopez H. A. , Chan S. , Fauchet P. M. , Bondarenko V. P. 
Published: April 2011

AbstractPorous silicon (PSi) was doped by Er using electromigration from a solution and converted to Er-doped silicon-rich silicon oxide (SRSO:Er) by partial thermal oxidation at 600–950°C following densification at 1100°C in an inert atmosphere. Room-temperature photoluminescence (PL) at ∼1.5 μm is intense and decreases by less than 20% from 12 K to 300 K. The PL spectrum of SRSO:Er reveals no luminescence bands related to Si-bandedgerecombination, point defects or dislocations, and shows that the Er3+ centers are the most efficient radiative recombination centers. A light-emitting diode (LED) with an active layer made of SRSO:Er was manufactured using a pre-oxidation cleaning step to increase the quality of the interface between SRSO:Er and the top electrode. Room temperature electroluminescence at ∼1.5 μm was demonstrated.
Photo- and Electro-Luminescence from Deuterium Terminated Porous Silicon
Authors: Matsumoto Takahiro , Masumoto Yasuaki , Koshida Nobuyoshi 
Published: April 2011

AbstractWe have studied the optical and the electrical properties of deuterium-terminated porous silicon. The photoluminescence spectrum was different from that of usual hydrogen-terminated porous Si despite both porous Si showing the same structure and the same absorption spectrum. In addition to these basic results, it is found that the replacement of hydrogen with deuterium reduces the degradation not only of photoluminescence but also of electroluminescence. The luminescence degradation mechanism will be discussed from the point of a photoinduced oxidation model.
Temperature-Dependent Photoluminescence of Silicon Nanocrystallites Prepared by Inert-Gas-Ambient Pulsed Laser Ablation
Authors: Umezu I. , Yamaguchi S. , Shibata K. , Sugimura A. , Yamada Y. , Yoshida T. 
Published: April 2011

AbstractThe inert-gas-ambient pulsed laser ablation technique is a promising method for preparing Si nanocrystallites. We measured the temperature dependence of photoluminescence (PL) spectra to investigate radiative and nonradiative recombination processes in the nanocrystallites prepared using this method. The Si nanocrystallites showed visible PL bands in the red (1.6 eV) and green (2.1 eV) spectral regions. The intensities of the red and green PL increased with decreasing temperature and then saturated below 80 K. This temperature dependence was compared with that of other photoluminescent Si materials. It was shown that the PL quantum efficiency of the Si nanocrystallites was larger than that of a-Si:H at high temperatures. One of the reasons for the difference in the temperature dependence between the Si nanocrystallite and a-Si:H is the change in the role of defects in the nonradiative recombination process.
Formation of Silicon Nanocrystallites by Electron Cyclotron Resonance Chemical Vapor Deposition and Ion Beam Assisted Electron Beam Deposition
Authors: Kim Eun Kyu , Choi Won Chel , Min Suk-Ki , Park Chong-Yun 
Published: April 2011

AbstractNano-crystalline silicon (nc-Si) thin films were directly deposited by electron cyclotron resonance chemical vapor deposition (ECR-CVD) and ion beam assisted electron beam deposition (IBAED) method. In the sample deposited by ECR-CVD, the room temperature photoluminescence originated from the nc-Si and the silicon-hydrogen bond were appeared. It was confirmed that the size of the nc-Si could be controlled up to about 3 nm with the low substrate temperature during the deposition process and then the hydrogen atoms play a very important role in the formation of the nc-Si. The IBAED method was also found to an useful technique for nc-Si formation by the control of ion beam power.
Photoexcitation of Si-Si Radiative Surface States in Nanocrystallites
Authors: Nayfeh M. H. , Rigakis N. , Yamani Z. 
Published: April 2011

AbstractRecently, intrinsic localized excitonic radiative surface states belonging to interacting dangling bonds of expanded, unstrained Si-Si dimers on the surface of nanocrystallites have been predicted. Those are connected, via a potential barrier, to the nonradiative delocalized excitonic states on the unexpanded, strained dimer. We present a theoretical analysis of the photoexcitation pathways involved in populating the radiative states. We include both direct above barrier, and indirect excitation from the photoexcited delocalized excitonic states via quantum tunneling and thermal activation. Our calculation gives an enhancement in the efficiency for sizes below a critical size of 1.4 nm, the size for which the outer trapped states become stable against tunneling and thermal activation. It is as if the material were changed from an indirect gap to a somewhat direct gap material. The results show that the photoluminescence exhibits a large Stokes shift resulting from the expansion of the radiative dimers. Moreover, the emission bandwidth is found to be quite wide especially for the ultra small crystallites (0.8 nm) where it encompasses nearly all of the visible spectrum, and the near infrared. Spectra simulated over size distributions are presented.
Characterization of Erbium Doped SiO2 Layers Formed On Silicon By Spark Processing
Authors: John John V. St. , Coffer Jeffery L. , Rho Young Gyu , Diehl Patrick , Pinizzotto Russell F. , Culp Thomas D. , Bray Kevin L. 
Published: April 2011

AbstractDeposition of a rare earth salt layer on a silicon substrate with subsequent spark processing yields a porous Si layer and SiO 2 cap doped with the rare earth ion. We have characterized luminescent Er-doped porous SiO2 on Si by scanning electron microscopy, energy dispersive Xray spectroscopy, as well as visible and near IR photoluminescence (PL) spectroscopies. Energydispersive x-ray maps indicate that the erbium concentration in the porous layer can be controlled by varying the molarity of the erbium solution deposited on the substrate prior to spark processing. Visible PL measurements reveal that the concentration of Er3+ is proportional to the resultant intensity of the visible fluorescence transitions; however, for the near IR fluorescence peak at 1.54 gim, self-quenching due to erbium clustering occurs at higher concentrations. Erbium-doped porous silicon layers can also be obtained by diffusion of an erbium salt into porous silicon formed by anodic etching of Si in hydrofluoric acid. Densification of the porous Si layers through high temperature oxidation after erbium diffusion forms erbium-doped SiO2 layers.
Time Decay Characteristics of the Yb3+- Related 0.98 μm Emissions in Porous Silicon
Authors: Kimura Tadamasa , Nishida Yasuhiro , Dejima Tohru , Saito Riichiro , Isshiki Hideo 
Published: April 2011

AbstractEnhanced emissions at 0.98 μm of Yb3+ ions (2F5/2 → 2F7/2) incorporated in porous silicon are obtained when the host porous silicon is pre-annealed in an O2 containing atmosphere. Time decay characteristics are measured for the Yb 3+-related 0.98 μm emissions as well as for the emissions of these host porous silicon between 20 K and 300 K. The decay of the Yb3+ peak at 20 K is characterized with a fast (˜ 30 μs) and a slow decay time (≤ ˜ 400 μs), whereas it is fitted with one slow decay time (˜ 390 μs) at 300 K. The results are explained in terms of two optical centers: one has a fast fluorescent lifetime with a large temperature quenching, and the other has a slow fluorescent lifetime which is nearly constant between 20 K and 300 K.