bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lattice Damage in Ion-Implanted Compound Semiconductors and Its Effect on Electrical Activation
Authors: Haynes T. E. , Morton R. , Lau S. S. 
Published: March 2011

ABSTRACTIn recent years, a number of experimental observations have indicated that interactions between mobile point defects generated during ion implantation play an important role in the damage production in Ill-V compound semiconductors, and particularly GaAs. This paper reviews a set of such observations based on ion channeling measurements of the lattice damage in GaAs implanted with Si ions. Selected independent observations are also surveyed to illustrate the importance of point-defect interactions. Taken together, these show that at least two contributions to the lattice damage must often be considered: a “prompt” contribution attributed to direct-impact amorphization, and a “delayed” contribution attributed to point-defect clustering. New measurements are then described which show the different effects that these two damage components have on the electrical activation in annealed, Siimplanted GaAs. The aim is to indicate the potential to exploit the balance between these two damage contributions in order to improve the electrical performance and reproducibility of ion-implanted and annealed layers. Finally, the applicability of these concepts to other ion species and other compound semiconductors (GaP and InP) is briefly discussed.
Modeling Dopant Diffusion in Gallium Arsenide
Authors: Deal M. D. , Hu C. J. , Lee C. C. , Robinson H. G. 
Published: March 2011

ABSTRACTWe have been developing models for our process simulators, SUPREM 3.5 and SUPREM-IV, for processes used in the fabrication of GaAs devices. Our initial experiments led to relatively simple models for diffusion of common dopants in GaAs, usually dependent only on temperature and the local dopant or carrier concentration. These models were incorporated into our first GaAs simulator, SUPREM 3.5. While these simple models were adequate for some process conditions, there are many cases where anomalous diffusion occurs and these models break down. The generally accepted diffusion mechanisms for n- and p-type dopants in GaAs have been shown to be the same as, or indistinguishable from, the models used for diffusion in silicon, and are therefore compatible with the diffusion algorithms used in SUPREM-IV. These algorithms include the effects of point defects. GaAs and eight of its dopants have recently been incorporated into SUPREM-IV and we have modeled, or are attempting to model, many of the anomalous diffusion phenomena using this simulator. These phenomena include uphill diffusion of implanted dopants, time dependent diffusion, implant energy dependent diffusion, and abnormal diffusion of grown-in dopants in MBE and MOCVD material.
Application of the Amphoteric Native Defect Model to Diffusion and Activation of Shallow Impurities in III-V Semiconductors
Authors: Walukiewicz W. 
Published: March 2011

ABSTRACTThe effects of heavy doping on the formation of charged point defects are considered. It is shown that the Fermi level dependent part of the formation energy of highly localized defects can be determined using a universal energy reference, common to all III-V compound semiconductors. The concept is used to analyze the electrical activity and diffusion of dopant impurities in these compounds. We present model calculations which explain the correlation between the maximum hole concentrations and the acceptor impurity diffusion in InP and in InGaAs alloys, doped with group II acceptors. The calculations account for the redistribution of the impurity atoms at the lattice matched InP/InGaAs interface. It is also demonstrated that an abrupt enhancement of the Fermi level induced defect formation is observed at the onset of highly degenerate statistics in heavily doped semiconductors.
Arbitrary Composition Profiles by MBE Using Desorption Mass Spectrometry
Authors: Evans K.R. , Kaspi R. , Cooley W.T. , Jones C.R. , Solomon J.S. 
Published: March 2011

ABSTRACTThe ability to produce semiconductor structures with arbitrary vertical composition profiles offers the device physicist new freedom in device structure design. We report on the incorporation of the in-situ sensor technique of desorption mass spectrometry (DMS) in a realtime feedback loop for the continuous control of desorption rates. Assuming previous knowledge of relevant incident fluxes, this technique provides for continuous determination of the composition of the outermost layer of the growing crystal. Using AlGaAs growth as an example, the Ga desorption rate Fd(Ga) is monitored continuously during growth, providing an accurate measure of Al-fraction in the topmost layer of the growing film. By comparing the measured and desired Fd(Ga), an error signal is generated and minimized by varying an appropriate growth parameter. Structures which are vertically graded in composition are produced by programming a varying Fd(Ga) versus time profile. Both substrate temperature Ts and incident arsenic flux Fi(As2) affect Fd(Ga) in a controllable way. Thus, two distinct control loops are constructed based on variable Ts and Fi(As2), respectively. As demonstration vehicles, graded AlGaAs structures with linear, parabolic, sawtooth, and sinusoidal compositional profiles have been produced and characterized. Additionally, we discuss some of the limitations of this technique and its applicability to other materials.
Electrical Characterization of Passivation Processes in Si-GaAs by Isothermal Photoinduced Transient Measurements
Authors: Dkiouak R. , Macia J. , Perez-Rodriguez A. , Gual J. , Morante J.R. 
Published: March 2011

ABSTRACTThe analysis of SI-GaAs passivated with different plasma treatments by isothermal PITS measurements shows the ability of this technique for the characterization of the electrical effects of the surface treatments. PITS spectra show, in addition to a midgap level assigned to EL2, a non exponential peak which strongly depends on the passivation process. This is related to the generation of defects during the surface processing, likely through the presence of interaction processes involving mid-gap related levels. The comparison between the spectra with different passivation conditions suggests the presence of ionized species in the plasma treatment and the fast growth rate of the passivation layer to determine a higher generation of these process related defects.
In Situ Flux Transient Monitoring and Correction During MBE Growth of Quantum Well Structures
Authors: Celii F. G. , Kao Y.-C. , Katz A. J. 
Published: March 2011

ABSTRACTShutter closure during MBE deposition causes source overheating and results in flux transients. These transients are particularly detrimental to the thickness and compositional accuracy of thin quantum well layers. In this paper, we document the effects of flux transients on growth of multiple quantum well (MQW) and resonant tunneling diode (RTD) structures, and demonstrate rudimentary transient correction by employing real-time flux detection.Reflection mass spectrometry (REMS) provides a convenient in situ method for MBE flux monitoring. The Group III partial pressures can be detected in the presence of Group V overpressure, and REMS is compatible with wafer rotation. We used REMS to characterize In, Al and Ga flux transients as a function of shutter closed time, cell flux and substrate temperature. Overshoot magnitudes up to 30% were observed. We verified the correspondence of REMS signal transients and effusion cell flux transients using GaAs/AlGaAs and InGaAs/lnAlAs MQW and test structures. We also successfully demonstrated flux transient correction by cell temperature ramping during MQW and RTD growth.
Creation of In-Plane Anisotropic Strain in GaAs/A1xGa1−xAs Multiple Quantum Well Structures
Authors: Lu Y. , Kuo H.C. , Shen H. , Taysing-Lara M. , Wraback M. , Pamulapati J. , Dutta M. , Kosinski J. , Sacks R. 
Published: March 2011

ABSTRACTThin film of GaAs/AlGaAs multiple quantum well (MQW) structure have been bonded to the lithium tantalate (LiTaO3) or calcium carbonate (CaCO3) substrates cut such that one of the linear thermal expansion coefficients almost matches that of the MQW while its orthogonal counterpart does not. By choosing the proper bonding and operating temperatures, in-plane anisotropic strain up to 0.3% has been achieved. The transmission spectrum shows an anisotropy in excitonic absorption which results in a polarization rotation of a light beam at normal incidence to the structure. The theoretical calculation is in agreement with the experimental results. Using the polarization rotation, we have demonstrated a novel MQW light modulator with an exceedingly high contrast ratio of 330:1.
Rapid Thermal Low Pressure Metalorganic Chemical Vapor Deposition of InP and Related Materials
Authors: Katz A. , Feingold A. 
Published: March 2011

ABSTRACTHigh quality InP and In0.53Ga0.67As undoped and Zn-doped layers were grown by means of rapid thermal low pressure metalorganic chemical vapor deposition (RTLPMOCVD) technique, using tertiarybutylphosphine (TBP) and tertiarybutylarsine (TBA), as the phosphorus and arsenic sources. The InP films were grown at a P:In ratios of about 75 and the InGaAs films were grown at a As:In ration of about 2, low temperatures at the range of 450-550°C, pressures it the range of 1-4 tons, and growth rates of 2-3 nm/sec. All the film growth conditions were optimized to yield defect-free layers with featureless morphology, which reflected at a minimum backscattering yield (Xmin) as low as 3.1% for the InP and 3.6% for the InGaAs. These films presented a good electrical properties, as well, with hole mobility of 4200 cm2/Vs for the undoped-InP layers and 75 cm2/Vs for the undoped-InGaAs layers.
Investigation of an Alternative Chemical Etchant for Mercuric Iodide Detectors
Authors: David Dominique C , Scyoc J. Van , Khudatyan Mardik , James R. B. , Anderson R. J. , Schlesingfer T. E. 
Published: March 2011

ABSTRACTAt present a 10% KI solution is commonly used as an etchant for HgI2 crystals. Recent photoluminescence (PL) spectra from such etched samples show that impurities contained in the KI solution dope the HgI2 during the etching process. Some of these dopants are known to cause carrier trapping in the detectors fabricated from the material. Thus, it is desirable to find an alternative etchant that does not create new defects in HgI2. Etchants studied here include deionized water, 10% potassium iodide (KI), methanol, and acetone. The results of acetone as an etchant reveal only small changes in the PL spectra after etching. Methanol etching causes the incorporation of a deep radiative recombination center in HgI2.
Recent Progress in The CdTe γ-Rays Detector Simulation
Authors: Manfredotti C. , Fizzotti F. , Ongaro C. , Vittone E. , Nastasi U. 
Published: March 2011

ABSTRACTRecently, we reported a simulation of spectroscopic performances of CdTe detectors by a Monte Carlo program ‘ISIDE’. The program was demonstrated to be extremely useful both for an exact simulation of the spectral response of CdTe to γy-rays and for a detailed understanding of the effect of physical and electronic parameters on the experimental performances. In the present work, the attention is focused on the various aspects of CdTe response to 57Co γ-rays, in an energy interval which is extremely interesting for practical applications of CdTe spectroscopy. Spectra are presented for different experimental conditions, particularly as far as electronics set up is concerned, in correlation with the relevant rise time distributions and with spatial distribution of interaction points in the detector. It is proved that in order to account for the rise times distributions as compared with the experimental ones, one must assume the presence of a dead region on the front of the detector. Moreover, a clear indication of what is needed in order to reach the best energy resolution in realistic conditions is given.
Use of Room Temperature Semiconductor Detectors for the Verification of Nuclear Material in International Safeguards Recent Advances
Authors: Arlt R. , Rundquist D.E. , Bot D. , Siffert P. , Richter M. , Khusainov A. , Ivanov V. , Chrunov A. , Petuchov Y. , Levai F. , Desi S. , Tarvainen M. , Ahmed I. 
Published: March 2011

ABSTRACTIn the paper the development and usage of radiation detection systems based on room temperature semiconductors are described. The detection systems are intended for use by safeguards inspectors to verify nuclear material. Because of their high intrinsic efficiency, these detectors have advantages compared to classical germanium or Nal detectors. Several measurement tasks which cannot be handled in an optimum manner by using standard detectors have been solved. The main problem in the application of room temperature semiconductor detectors is the limitation in the availability of large detector volumes.
Pulse Processing for Planar Cadmium Telluride Detectors
Authors: Richter M. , Hage-Ali M. , Kuznicki Z.T. , Siffert P. 
Published: March 2011

Planar CdTe detectors with different performances for gamma radiation detection have been investigated. The detector internal electric field was analyzed by means of time-of-flight experiments. The correlation of the results with the current-voltage characteristics of the samples, their risetime distribution for different gamma irradiation and, eventually, the shape of detected gamma spectra led us to a detector model based on the theory of space charge limited current.Using this model, we try to explain operation and failure of trapping loss correction methods for the different detector groups.
Mathematical Model for the Simulation of Crystallization of CdTe in a vertical Bridgman Furnace.
Authors: Steer Ch. , Hage-Ali M. , Siffert P. 
Published: March 2011

ABSTRACTTemperature measurements in a crystal growth ampoule of CdTe (Cadmium Telluride) are very difficult. Mathematical simulation is a very powerful tool to predict the behavior and temperature distribution during crystal growth. We applied this technique to the bulk growth of large single crystals of CdTe. The simulation revealed that for CdTe, it is possible to create a convex interface shape during growth, necessary for single crystal growth. The controlling parameter is the temperature profile along the ampoule. The temperature gradient is rather meaningless, as we can show with our simulations.We will present some crystals grown under good and bad thermal conditions.
Fast Diamond Photoconductors
Authors: Pochet T. , Brullot B. , Galli R. , Rubbelynck C. 
Published: March 2011

ABSTRACTPreliminary results on the response of type Ib and IIa diamond photodetectors to fast laser pulse exposures at 265 and 530 nm are presented. The influence of the applied bias, the laser wavelengths and the light intensity on the detector sensitivity is studied. Also, recent measurements with 1.25 MeV gamma ray pulses are reported.
Improvements in Thallium Bromoiodide Photodetectors for Scintillation Spectrometers
Authors: Zhang J.G. , Cirignano L. , Daley K. , Squillante M.R. 
Published: March 2011

ABSTRACTThallium bromoiodide, a tuneable band gap semiconductor system, was investigated as a photodetector for scintillation spectrometers. Extensive zone refining of starting materials, based on numerical simulations, considerably enhanced the electrical resistivity to 1011 Ωcm. In addition, accelerated crucible rotation technique (ACRT) crystal growth and after-growth annealing have improved the charge carrier mobility-lifetime product. However, a relatively low signal-to-noise ratio due to a high dielectric constant and relatively low quantum efficiency continues to be an obstacle to achieving high performance, large area T1BrxI1−xphotodetectors.
Studies of Charge Collection in GaAs Radiation Detectors
Authors: Berwick K , Brozel M R , Butiar C M , Cowperthwaite M , Hou Y 
Published: March 2011

ABSTRACTThe behaviour of the charge collection efficiency of particle detectors fabricated from Semi-Insulating (SI) Liquid Encapsulated Czochralski (LEC) GaAs as a function of applied bias is investigated for alpha particles and it is shown that it cannot be explained by simple models that assume a uniform electric field across the detector. To investigate this the electric field within the SI GaAs has been studied. We have attempted to correlate the measured charge collection efficiency with the observed field distributions. Some correlation is found but other effects may also be present.
Improved Quality of Bulk II-VI Substrates for HgCdTe and HgZnTe Epitaxy
Authors: Sen Sanghamitra , Stannard John E. 
Published: March 2011

ABSTRACTSingle crystals of CdTe or dilute alloys of Cdl−y ZnyTe (y ≤ 0.04) and CdTel−zSez (z ≤ 0.04) with low defect density, high purity and large single-crystal area (>30 cm2) are required as substrates for high-quality epitaxial Hgl−xCdxTe thin films in the infrared (IR) detector industry. Bridgman or gradient freeze is the most common technique used for commercial production of these materials because of its success in producing large area substrates of good quality and reproducibility. For epitaxial growth of Hg1−xZnxTe, which has been of considerable interest in recent years as an IR detector material, the substrate of choice has been Cd0.80Zn0.20Te, for lattice matching with long wavelength Hg1−xZnxTe epitaxial layers (x = 0.13–0.14). The primary focus of this paper is on CdZnTe which is currently the preferred substrate material and most widely used for both HgCdTe and HgZnTe epitaxy. This paper reviews the current status of bulk substrate technology for IR detector applications, highlighting critical issues and essential research areas for further improvement of these materials.
Mapping of Defects in Metal-Semiconductor-Metal (MSM) Detectors in Hg1−xCdxTe by Nuclear Microprobe
Authors: Leech Patrick W. , Dooley Sean P. , Jamieson David N. 
Published: March 2011

ABSTRACTThe incidence of compositional and structural inhomogenieties in MSM detectors based on Hg1−xCdxTe/GaAs and Hg1−xCdxTe/GaAs/Si has been examined by nuclear microprobe. With a 2 MeV He+ beam focussed to ≥5 μm, the microprobe has demonstrated the capability for RBS channelling in the active region of a Hg1−xCdxTe device and the imaging of defects by Channelling Contrast Microscopy (CCM). A series of linear growth defects in some Hg1−xCdxTe devices were identified using CCM. The channelling RBS spectra from these regions have shown an increase in χmin compared with the surrounding high quality crystal. The occurence of these defects was associated with a degradation in the performance of affected devices in an array. RBS spectra have also revealed the presence of an anomalous CdTe layer, correlating with a significant reduction in dark current and increase in breakdown voltage of these devices. RBS channelling of individual devices has identified differences in χmin between arrays which were prepared under equivalent conditions of growth and processing.
Quality of Bulk Cdte Substrates and Its Relation to Intrinsic Defects
Authors: Meyer B. K. , Hofmann D. M. , Stadler W. , Emanuelsson P. , Omling P. , Weigel E. , MÜller-Vogt G. , Wienecke F. , Schenk M. 
Published: March 2011

ABSTRACTBoth the cadmium vacancy (Vcd) and the tellurium vacancy (VTe) in CdTe are identified by means of electron paramagnetic resonance (EPR). The VCd is a double acceptor and the EPR spectrum is observed in its single negative charge state. The symmetry is found to be trigonal, which can be explained in a model in which the hole occupies a dangling bond t2 orbital and the orbital degeneracy is removed by a static Jahn-Teller distortion. The hyperfine interaction shows that the hole is localised on one of the four Te neighbours. The EPR spectrum of VTe+ reveals cubic (unperturbed) symmetry and the hyperfine structure shows that the unpaired electron is equally spread over the four Cd neighbours.Photo-EPR measurements locate the 0/+ state of VTe at Ev + 0.2 eV and the 2−/− acceptor level of VCd to be situated less than 0.47 eV above the valence band.
Recent Developments in High Resistivity Detector-Grade CdTe
Authors: Hage-Ali M. , Siffert P. 
Published: March 2011

ABSTRACTWe present a brief review of results concerning the doping or compensation of CdTe by different elements like halogen, group IV, hydrogen and 3d transition elements for high resistivity materials. Comparison with theoretical models and discussion of results under this light is provided.
Bulk Defects and Radiation Damage in Detector Grade Silicon
Authors: Walter J. , Garber W. , Wunstorf R. , Bugg W. , Harvey J. , Casson W. 
Published: March 2011

ABSTRACTThe importance of bulk defects in Si to the performance of Si radiation detectors is discussed and the current state of knowledge about deep level defects, including those induced by radiation damage, is briefly reviewed. The importance and origins of the fluctuations in the spatial distribution of the shallow point defects which determine the uncompensated net impurity density are discussed and information on this problem in FZ silicon, multipass FZ silicon, neutron transmutation doped Si, and radiation damaged Si is presented and compared to what should be expected on the basis of simple modeling. A new model for radiation damage induced changes in the net uncompensated impurity density is reviewed and compared to experimental data on fast neutron damage in Si.
Charge Collection Processes in a-Si:H p-i-n Detectors
Authors: Pochet T. 
Published: March 2011

ABSTRACTCharge induced as a function of time in a-Si:H p-i-n detectors by protons having energies ranging between 5 and 12 MeV have been studied. A multiple trapping transport model is developed in order to explain the non saturation of the collected charge with bias and evidence of a bias dependent recombination process is shown. The dependence of the total induced charge (the detector efficiency) with bias can be expressed by an Onsager function with a thermalization distance of 34 Å.
TiSi2 Formation on Submicron Polysilicon Lines: Role of Line Width and Dopant Concentration
Authors: Ganin E. , Wind S. , Ronsheim P. , Yapsir A. , Barmak K. , Bucchignano J. , Assenza R. 
Published: March 2011

ABSTRACTWe report on a study of the effects of dopant concentration and linewidth on the formation of TiSi2 on polysilicon. The transformation from the C49 phase to the C54 phase is inhibited by a high concentration of either phosphorus or arsenic in blanket polysilicon films. For sub-half-micron lines, patterned in polysilicon doped with As or P, agglomeration is the key factor in the inability to produce low resistance silicide. The result is a critically shrinking process window for the attainment of low resistance VLSI interconnects.
Optical Fiber Pyrometry with in-Situ Detection of Wafer Radiance and Emittance—Accufiber's Ripple Method
Authors: Fiory A. T. , Schietinger C. , Adams B. , Tinsley F. G. 
Published: March 2011

ABSTRACTA two-channel optical-fiber pyrometry technique for simultaneous measurement of thermal radiance and emittance was used to measure and control the temperature of silicon wafers heated by quartz-halogen-tungsten lamps in various rapid-thermal processors, including an A.G. Associates Heatpulse. The ripple method dynamically determines emittances by sensing time-dependent components in radiation from the lamps and radiation reflected by the wafer surface. Wafers were coated with films of various textures and patterns to test the technique over a range of surface emittances spanning about an order of magnitude. Temperature accuracies of at least ±5°C are achievable from 650°C to 1050°C, and above, for pyrometry at lμm wavelength.