bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stable Pt/Ge/Au Ohmic Contact to N-GaAs with a Ta-Si-N Barrier
Authors: Chen J. S. , Kolawa E. , Ruiz R. P. , Nicolet M-A. 
Published: March 2011

ABSTRACTA Pt/Ge/Au contact of the structure: <n-GaAs>/Pt(17nm)/Ge(25nm)/Au(43nm), overlaid with a Ta-Si-N barrier layer and a Au metallization layer has a contact resistivity, ρc, of 3.7×10−6 Ωcm2 after annealing at 450°C for 15 min. After aging at 450°C for 60 h, ρc slightly degrades to 5.5×10−6 Ωcm2 while the surface keeps smooth. When alloyed at 550°C for 15 min, ρc is 1.8×10−6 Ωcm2 and stays about the same value after annealing at 550°C for 1 h. Without the Ta-Si-N barrier and the Au overlayer, the Pt/Ge/Au contact alone is also ohmic after annealing at 450°C for 15 min but with a ρc of ∼10−5 Ωcm2 while the surface morphology deteriorates significantly after aging at 450°C for 20 h.The thermal reactions of this Pt/Ge/Au contact on GaAs, with or without a Ta-Si-N barrier layer, are investigated by backscattering spectrometry, x-ray diffraction, and transmission electron microscopy in conjunction with energy dispersive analyses of x-rays. For all samples, the main reaction products after annealing at 450°C for 15 min are Au7Ga2, and PtGe:As, a PtGe phase that also contains arsenic. The product phases are randomly distributed within a laterally uniform reacted layer when the Pt/Ge/Au contact is covered by a Ta-Si-N layer. Without the Ta-Si-N barrier layer, a small arsenic loss and a Ga-rich phase (probably Gaoxides) on the contact surface are observed after annealing at 450°C. In this case, the surface and contact-semiconductor interface are more faceted than with a Ta-Si-N barrier layer.
The Study of TiWN Schottky Contacts on n-Ga0.51 In0.49P
Authors: Chang Edward Y. , Lai Yeong-Lin , Lin Kuen-Chyuan , Chang Chun-Yen , Juang F. Y. 
Published: March 2011

ABSTRACTThe first study of the TiW nitrides (TiWNx) as the Schottky contact metals to the n type Ga0.51In0 49P has been made. The Ga0.51 In0.49P epitaxial layer was successfully grown on the GaAs substrate by LP-MOCVD to form a lattice-matched heterostructure. The RF-magnetron sputtering system was utilized for the nitride deposition. The thermal stability of the nitride films were studied using rapid thermal annealing (RTA) method. Both the electrical characteristics and the materials characteristics were investigated. The materials properties of the nitride films were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), and Auger electron spectroscopy (AES). The TiWNx Schottky contacts demonstrate excellent electrical and physical characteristics, even after high temperature annealing. The barrier heights range from 0.81 to 1.05 eV depending on the content of the nitrogen and the annealing conditions. The XRD and AES results show no indication of interaction at the TiWNX/GaInP interface of both as-deposited and annealed samples. The outstanding characteristics of the contact were attributed to the high bandgap nature of the Ga0.51In0.49P and the incorporation of nitrogen into the TiW films.
Metallurgical and Electrical Properties of Capped Au-based Metallizations on GaAs
Authors: Lin X. W. , Piotrowska A. , Kaminska E. , Liliental-Weber Z. , Washburn J. 
Published: March 2011

ABSTRACTGold-based contacts on GaAs, i.e., Au(Te)/n-GaAs, Au(Ge)/n-GaAs, and Au(Zn)/p- GaAs, were annealed with or without an Al2O3 cap, in order to examine the effects of capping on their metallurgical and electrical properties. Current-voltage measurements showed that ohmic contact can be formed for all the metallizations, except capped Au(Te) which remained nonohmic even after annealing up to 480°C. Transmission electron microscopy and x-ray diffraction observations showed that the reactions between a contact and GaAs can be strongly affected by a capping layer. For all uncapped contacts, annealing generally resulted in growth of Au-Ga compounds and nonuniform contact morphology, whereas capped Au(Ge) and Au(Zn) contacts were stable and retained flat interface with GaAs. Capped Au(Te) was found to be unstable, reacting extensively with GaAs, due to the presence of Te. Electrical data are explained in terms of the doping model for ohmic contact formation.
Layer Disordering and Carrier Concentration in Heavily Carbon-Doped AlGaAs/GaAs Superlattices
Authors: You H. M. , Tan T. Y. , Gösele U. M. , Höfler G. E. , Hsieh K. C. , Holonyak N. , Lee S.-T. 
Published: March 2011

ABSTRACTAl-Ga interdiffusion, carbon acceptor diffusion, and hole reduction were studied in carbondoped Al0.4Ga0.6As/GaAs superlattices (SL). Al-Ga interdiffusion was found to be most prominent for Ga-rich annealing, with the hole concentrations in the SL almost intact during annealing. For As-rich annealing, the interdiffusivity values, DAI.Ga, are in approximate agreement with those predicted by the Fermi-level effect model, and the hole concentrations in the SL decreased dramatically after annealing. By analyzing the measured hole concentration profiles, it was found that both carbon acceptor diffusion and reduction have occurred during annealing, with both depending on As4 pressure values to the one quarter power. These As4 pressure dependencies indicate that carbon diffuses via the interstitial-substitutional mechanism while hole reduction is governed by a precipitation mechanism.
Sulfur Passivation of InP and GaAs
Authors: Kapila A. , Si X. , Malhotra V. 
Published: March 2011

ABSTRACTPassivation of electronic defect states at the SiNx/InP and the SiNx/GaAs interfaces has been achieved using both ‘wet’ (ammonium and phosphorous polysulfide solutions) and ‘dry’ (H2S gas) sulfur treatments. The passivated surfaces are encapsulated by depositing SiNx overlayers at ∼ 200 °C using the electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) technique. The capacitance-voltage (C-V) characteristics of metal-insulatorsemiconductor (MIS) capacitors indicate substantial reduction in the density of interface defects. Schottky diodes, fabricated in sulfur-treated n-GaAs, also exhibit significant improvements. The H2S-treatment provides better reproducibility and uniformity when compared with the ‘wet’ sulfide treatment of the surfaces.
Deposition of Tin by Electron Cyclotron Resonance - Metal Organic Molecular Beam Epitaxy
Authors: Wisk P. W. , Abernathy C. R. , Pearton S. J. , Ren F. , Katz A. , Bohling D. A. 
Published: March 2011

ABSTRACTWe have investigated the feasibility of depositing TiN from nitrogen plasmas by Electron Cyclotron Resonance – Metal Organic Molecular Beam Epitaxy (ECR-MOMBE). Growth rate, index of refraction and resistivity were evaluated as a function of growth temperature and group V flow. It was found that TiN could be deposited at reasonable growth rates on either GaAs or Si substrates. However, the resistivity of the materia is quite high, >1700 µΩ-cm, probably because of significant carbon uptake into the layers.
Chemical Beam Epitaxy Grown Indium Gallium Arsenide Tunnel Junctions
Authors: Medelci N. , Bensaoula A. , Vilela M. F. , Freundlich A. 
Published: March 2011

ABSTRACTp+/n+ In0.53Ga0.47As tunnel junctions with room temperature peak to valley ratio of 9:1 are demonstrated. The device structures were grown on both InP and GaAs (4% lattice mismatch) using Chemical Beam Epitaxy (CBE). Be and Si were used as dopants. The devices grown on InP exhibit room temperature peak current in excess of 1000 A/cm2. The peak current of 452 A/cm2 achieved on lattice mismatched material (GaAs) is comparable to the highest results previously reported on lattice matched material (InP). Finally, The device characteristics and the influence of different fabrication steps on the performance of these devices are discussed based on temperature dependent I-V measurements.
High Gain, Low Noise InP Heut for Millimeter-Wave Application
Authors: Yuen C. , Pao Y. C. , Chiang N. , Bechtel N. G. 
Published: March 2011

ABSTRACTLattice matched InP HEMT has demonstrated superior gain and noise figure performance compared to the AlGaAs HEMT and PHEMT. The gain and noise figure advantages of the InP HEMT have been transferred to the excellent MMIC performance in the millimeter-wave region.
Fabrication of High Quality MOS Devices for Application in Hazardous Environments Based on RTP Gate Dielectrics with In Situ RTCVD of Polysilicon Gates
Authors: Fröschle B. , Bruemmer H.P. , Lang W. , Neumeier K. , Ramm P. 
Published: March 2011

ABSTRACTProcess modules for MOS gate fabrication were developed which can be completed subsequently in one RTP reactor: atmospheric process sequences for gate oxides and oxynitrides as well as low pressure chemical vapor deposition of polysilicon (RTCVD). Prior to the Rapid Thermal Oxidation (RTO), the wafers were treated with a Rapid Thermal Cleaning process (RTC) in H2/Ar ambient. After the desoxidation step the RTO was done in O2/H2/Ar followed by an anneal (RTA) for the gate oxide or a nitridation in NH3 (RTN) and reoxidation for the oxynitrides, respectively. The polysilicon gate electrode was fabricated either by RTCVD in situ or in a conventional furnace reactor. The two-step RTCVD process resulted in a very good thickness uniformity for the polysilicon layers of 3% (3mm from the edge). The influence of the process variations on breakdown field, fixed oxide charge, interface state density, flatband voltage, and threshold voltage of the different types of gate dielectrics was investigated. The charges and voltages were determined by LF-HF CV measurements. In order to characterize the radiation tolerance of electronic devices, radiation induced flatband and threshold voltage shifts as well as the build up of interface charges were determined. The irradiation was performed at a Co - 60 gamma source. Breakdown fields in the range of 19 MV/cm, interface state densities of less than 109 eV−1cm−2, and radiation induced threshold voltage shifts below 0.1 V after 1.5 Mrad(Si) were obtained.
Reliability of Carbon Doped Base AlGaAs/GaAs HBTs as a Function of Collector Current
Authors: Prasad S.J. , Hultine E. 
Published: March 2011

ABSTRACTThe HBTs used in this study were grown by OMVPE. The base was carbon doped to 3×1019 cm−3 and the base thickness was 500Å. Several 3μ ×10μ HBTs were biased at Ic =2,4 and 10mA (VCE=2V) and maintained at TA=125°C. Based on 1000 hours of operation at 125°C, Ic =2mA is safe, Ic =4mA is marginal and Ic =10mA is fatal.
Epitaxial Growth, Fabrication, and Performance of Ingaas Strained Quantum Well Laser Structures
Authors: Hobson W. S. 
Published: March 2011

ABSTRACTThere is considerable interest in InGaAs/GaAs strained quantum well lasers for applications within the 0.9 to 1.1 μm wavelength range, such as high power lasers for Efdoped fiber amplifiers and rare-earth-ion solid state lasers, obtaining blue-green laser emission by frequency doubling, and optoelectronic integrated circuits. Epitaxial growth of these structures by organometallic vapor phase epitaxy, molecular beam epitaxy, and gas source molecular beam epitaxy will be discussed. The relative merits of AlGaAs and InGaP cladding layers will be examined with respect to growth challenges, laser processing and performance, and device reliability. Several device structures which provide transverse and lateral confinement will be reviewed. Reduction of the transverse far-field angle, which improves fiber coupling efficiency, can be accomplished through the use of periodic index separate confinement and depressed index cladding heterostructures. The performance of ridge waveguide lasers, which require accurate control of the ridge height, can be improved through the incorporation of etch-stop layers, either InGaP or AlAs, in the AlGaAs cladding layer. Nonplanar growth over mesas etched into the substrate is a convenient method to obtain buried heterostructure lasers. Carbon-doped planar InGaAs/AlGaAs lasers, using CC14 as an extrinsic dopant, have been fabricated with an impurity-induced layer disordering process. Microcylinder lasers have been fabricated out of InGaAs/InGaP layer structures.
Defects in Silver-Doped Mercuric Iodide Crystals and their Effect on X-Ray and Gamma-Ray Detector Performance
Authors: James R. B. , Bao X. J. , Schlesinger T. E. , Cheng A. Y. , Gerrish V. M. 
Published: March 2011

ABSTRACTThe processing steps associated with purification of source material, crystal growth, and attachment of electrical contacts can introduce defects into mercuric iodide (HgI2) that degrade the performance of detectors. We have employed low-temperature photoluminescence (PL) spectroscopy to study radiative recombination centers in the interfacial region between a thin semitransparent film of silver and mercuric iodide. The Ag film was found to introduce a new broad emission band centered at 5490 Å in the photoluminescence spectrum of HgI2. This PL feature can be used as a signature to identify the existence of Ag as a contaminant in HgI2crystals and detectors. Experiments were also conducted on mercuric iodide surfaces that had been doped with silver, and the results showed that Ag is a rapid diffuser in bulk HgI2. Detectors with silver electrodes were also fabricated and tested using an americium-241 gamma-ray source. Large increases in the leakage currents were observed for the Ag-doped HgI2devices, indicated that Ag impurities are electrically active in HgI2. These measurements show that silver is unacceptable as an electrode material for mercuric iodide x-ray and gamma-ray detector applications. In addition, they reveal that caution must be taken during handling of mercuric iodide source material, crystals, and detectors to avoid contact with silver, silver compounds, or with any material that contains silver as a contaminant.
Incorporation of Extrinsic Defects in HgI2 During Detector Fabrication
Authors: Van Scyoc J.M. , Schlesinger T.E. , James R.B. , Cheng A.Y. , Ortale C. , van den Berg L. 
Published: March 2011

ABSTRACTThe incorporation of extrinsic defects into mercuric iodide substrates during detector fabrication can be extremely detrimental to device performance. In particular, extrinsic defects can act as trapping and recombination centers, and they can reduce charge collection efficiencies, decrease gt product, or contribute to polarization effects in nuclear detectors. In this paper we present results of processing, photoluminescence, and electromigration experiments that clearly show that extrinsic defects can be incorporated in mercuric iodide during detector fabrication. By observing the luminescence features characteristic of Cu and Ag in mercuric iodide, we show that both these materials are taken up by mercuric iodide crystals during etching with KI if the etching solution is contaminated with these elements. The migration of material from contacts into the crystal, as shown by resistance measurements, is also presented. We infer from this work that other defects which are detrimental to device performance may also be incorporated in mercuric iodide if insufficient care is taken during device fabrication. Suggestions are therefore made as to some of the precautions that must be taken in order to realize the highest quality detectors.
X-Ray Analysis of Alpha Mercuric Iodide Crystal Structure and Processing Effects
Authors: Keller L. , Wang E.X. , Cheng A.Y. 
Published: March 2011

ABSTRACTX-ray topography and rocking curve experiments were performed on α-mercuric iodide samples. As-grown crystals were examined for intrinsic defects and crystallinity. Orientation of certain defects depends on the direction of crystal growth. The propagation of as-grown crystalline features was documented. The extent of crystal damage introduced during various steps of device fabrication such as sawing, polishing, etching and contact deposition was explored. Coefficients of linear thermal expansion of α33 = 54 ± 5 (10−6/°C) along the tetragonal c-axis, \001] direction and ±ll = 11 ± 4 (10−6/°C) in the \100] direction were measured.
CdTe:Cl and CdTeSe:Cl Single Crystals Application for Radiation Detectors
Authors: Meyer B.K. , Hofmann D.M. , Stadler W. , Salk M. , Eiche C. , Benz K.W. 
Published: March 2011

ABSTRACTWe report on electrical and optical properties of vertical Bridgman grown Cl-doped CdTe including the ternary compositions Cd0.9Zn0.1Te and CdTe0 9Se0.1 with respect to application as a radiation detector. Based on Hall effect measurements, photoinduced current spectroscopy (PICTS) and photoluminescence we infer that high resistive material with good performance is controlled by deep level defects. The resistivity is calculated as a function of the shallow acceptor concentration (Cl-A-centers) with the conclusion that a deep donor state at mid gap must be present.
An Ultra Low Noise Preamplifier for Room Temperature X-Ray Detectors
Authors: Bertuccio G. , Rehak P. , Xi D.M. 
Published: March 2011

ABSTRACTA new circuital configuration for the charge amplifier is presented. By means of a double feedback loop, the input field-effect transistor can operate with its gate junction sligtly forward biased, collecting the detector current and discharging the feedback capacitor. The feedback resistor is so avoided and no resetting device or circuit is required for the preamplifier operation. The noise is limited by the input transistor, an equivalent noise charge of 19.5 r.m.s. electrons has been measured at room temperature by employing a commercial JFET.
Characterization of Cvd Diamond Films by Optical Spectroscopies
Authors: Ager Joel W. , Han Sung , Wagner Ron S. , Pan Lawrence S. , Kania D.R. , Lane Stephen M. 
Published: March 2011

ABSTRACTRaman and photoluminescence spectroscopy was used to investigate radiation damage by 5 MeV He+ ions at room temperature in prototype CVD-diamond detector material. Amorphization of the diamond is not observed at fluences up to 8×1015 cm-2. A threshold behavior is seen in the formation of the H3 vacancy-dinitrogen color center. The defect is not observed for fluences in the range 1.6×1012 to 1.6×1013 cm-2; a linear behavior increase in H3 intensity is observed over the range 1.6×1014 to 1.6×1015 cm-2. The formation mechanism of the H3 color center under He+ irradiation involves a self-annealing effect that allows vacancies to diffuse to, and complex with, nitrogen complexes.
High-Purity Germanium Technology for Gamma-Ray and X-Ray Spectroscopy
Authors: Darken L.S. , Cox C. E. 
Published: March 2011

ABSTRACTHigh-purity germanium (HPGe) for gamma-ray spectroscopy is a mature technology that continues to evolve. Detector size is continually increasing, allowing efficient detection of higher energy gamma rays and improving the count rate and minimum detectable activity for lower energy gamma rays. For low-energy X rays, entrance window thicknesses have been reduced to where they are comparable to those in Si(Li) detectors. While some limits to HPGe technology are set by intrinsic properties, the frontiers have historically been determined by the level of control over extrinsic properties. The point defects responsible for hole trapping are considered in terms of the “standard level” model for hole capture. This model originates in the observation that the magnitude and temperature dependence of the cross section for hole capture at many acceptors in germanium is exactly that obtained if all incident s-wave holes were captured. That is, the capture rate is apparently limited by the arrival rate of holes that can make an angular-momentum-conserving transition to a s ground state. This model can also be generalized to other materials, where it may serve as an upper limit for direct capture into the ground state for either electrons or holes. The capture cross section for standard levels σS.L. is given bywhere g is the degeneracy of the ground state of the center after capture, divided by the degeneracy before capture. Mc is the number of equivalent extrema in the band structure for the carrier being captured, mo is the electronic mass, m* is the effective mass, and T is the temperature in degrees Kelvin.
Investigation of Lead Iodide Crystals for Use as High Energy Solid State Radiation Detectors
Authors: David Dominique C. , James R. B. , Feemster H. , Anderson R. , Antolak A. J. , Morse D.H. , Pontau A. E. , Jayatirtha H. , Burger A. , Bao X. J. , Sch-Lesinger T. E. , Bench G. S. , Heikkinen D. W. 
Published: March 2011

ABSTRACTSignificant developments have occurred in the technology of room-temperature PbI2 nuclear sensors which lead to some improvements in the detection of high energy gamma-rays. Discussion of crystal growth, purification, monitoring purification, and detector processing are reviewed as they relate to device performance.
Processing and Characterization of HgBrxI2−x Radiation Detectors
Authors: Zhou C. , Squillante M. R. , Moy L. P. , Bennett P. 
Published: March 2011

ABSTRACTThis paper reports our recent work on the crystal processing, structural and optical characterization of HgBrxI2−x nuclear radiation detectors. To understand the electrical and optical properties of the detectors, we measured the energy gap of HgBrxI2−x as a function of the Br/I ratio. The energy band of this ternary semiconductor compound can be modulated from 2. 1eV (HgI2) to 3.4eV (HgBr2) by adjusting its chemical composition. This energy scope covers a wavelength spectrum between 365nm and 596nm, much of the visible spectrum. Nuclear and photoconductive detectors were fabricated from HgBrxI2−x single crystals and the responses of these devices were investigated with different radiation sources (241Am, 137Cs).
Excess Carrier Lifetimes in (HgCd)Te Grown by Mocvd Interdiftused Multilayer Process
Authors: Mitra P. , Schimert T. R. , Tyan Y. L. , Brouns A. J. , Case F. C. 
Published: March 2011

ABSTRACTTransient lifetime measurements on p- and n-type Hg1-xCdxTe epitaxial films, grown by the MOCVD-interdiffused multilayer process (IMP) on CdTe and CdZnTe, are reported. Lifetimes have been measured on undoped n-type, vacancy and arsenic doped p-type (HgCd)Te for x-values of 0.20-0.28 over the 25K-300K temperature range. Lifetime characterization has been carried out primarily by non-contact transient millimeter wave reflectance as well as by standard photoconductive decay. It is shown that Auger limited lifetimes are achievable in undoped n-type material. N-type lifetime results are analyzed within the framework of a multilevel Shockley-Read model which provide insight into the nature and density of defect states in the material. In p-type (HgCd)Te, for the same carrier concentration, longer lifetimes are obtained by As-doping than in vacancy doped material.
Twinning Effects in Hg1−xCdxTe (x∼0.2) Grown by Thm in The <111> Direction
Authors: Weiss Eliezer , Kedar Ehud , Mainzer Nili 
Published: March 2011

ABSTRACTHg1−xCdxTe crystals with x∼0.2 were grown by the traveling heater method (THM), in either the [111]A or [111]B directions, using oriented CdTe seeds. Twins are sometimes formed during the growth of these crystals. In crystals grown in the [11]A direction the twins, of orientation [511]B, are constantly growing at the expense of the original [111]A oriented grain. Growth in the [111]B direction, on the other hand, suppresses the growth of the twin domain. Photodiodes and capacitors realized on the (111)A plane are markedly superior to those on the twin plane, (511)B. The difference is due to higher fixed charge and larger fast surface state densities in the case of the (511)B plane. These effects are explained by the lattice structures in the {111} and {511} planes and their possible influence on surface reactivity.