bluuebunny/crossref_metadata_2025_split huggingface dataset:
Real-time Optical Monitoring of GaxIn1−xP/GaP Heterostructures on Silicon
Authors: Dietz N. , Rossow U. , Aspnes D. E. , Sukidi N. , Bachmann K. J. 
Published: April 2011

AbstractIn this paper we report the combined application of p-polarized reflectance spectroscopy (PRS), reflectance difference spectroscopy (RDS), and laser light scattering (LLS) to investigate the heteroepitaxy of GaxIn 1−xP/GaP on Si by pulsed chemical beam epitaxy (PCBE) with tertiarybutylphosphine (TBP), triethylgallium (TEG), and trimethylindium (TMI) precursors. Both, PRS and RDS follow the growth process with submonolayer resolution utilizing a periodic fine structure signal, which is caused by a periodic alteration of thickness and composition of an ultra-thin surface reaction layer during the periodic TEG and TBP exposure of the surface. After the transition from GaP growth to GaxIn 1−xP growth, the RDS oscillations are reoriented after about five precursor cycles in a new oscillation periodicity, where the response to the TBP pulse has the opposite direction. The ratio of the changes in the amplitudes of RDS signals as a response to TEG and TMI surface exposure is used to estimate the composition fo GaxIn 1−xP. The PRS fine structure is maintained after switching to GaxIn 1−xP growth with a separate feature for each TEG and TMI surface exposure. The amplitude ratio of these features changes during growth.
Temperature Measurements Using In Thermocouple In The Mocvd Rotating Disk Reactors
Authors: Gurary A. I. , Stall R. A. 
Published: April 2011

AbstractRotating Disk Reactors used for Metalorganic Chemical Vapor Deposition have evolved into a leading manufacturing technology for several materials, including nitrides, compound semiconductors, metals, and oxides. One of the major issues to be resolved in bringing this technology into routine high yield manufacturing has been precise and repeatable wafer temperature measurement and control. The conventional approach to the rotating wafer temperature measurements by a stationary thermocouple located near the rotating wafer carrier suffers from low accuracy and repeatability. We have implemented a rotating thermocouple with a junction located close to the wafer for the temperature measurements in the MOCVD Rotating Disk Reactor. This approach allowed us to obtain reliable and accurate wafer temperature measurements with minimum dependence upon variable process parameters and to protect the thermocouple from degradation in the aggressive reactor environment. The temperature difference between wafer and thermocouple for the rotating and stationary thermocouple designs as a function of process parameters will be discussed.
Real-Time Monitoring Of GaAs(100) Etching By Surface Photoabsorption
Authors: Eng Joseph , Fang Hongbin , Su Chaochin , Vemuri Sujata , Herman Irving P. , Bent Brian E. 
Published: April 2011

AbstractSurface photoabsorption (SPA) has been applied to monitor, in real time, the surface of GaAs(100) during chemical dry etching by a molecular beam of HCl. Changes in the HCl flux to the surface at a constant temperature (840 K) have been used to induce changes in the Ga:As ratio on the surface. These changes in surface stoichiometry have been detected in situ via SPA measurements of the transient fractional change in the reflectance of p-polarized, 488 nm light that is incident onto the surface near the pseudo-Brewster angle. On the basis of results from prior applications of SPA to the study the atomic layer deposition of GaAs, the changes in the SPA signal as a function of the etching parameters can be correlated with changes in the relative surface densities of Ga and As. The findings are confirmed by independent determinations of the changes in surface stoichiometry made by measuring the time-integrated difference in the fluxes of Ga- and As-containing etching products evolved from the surface as a function of the HC1 flux.
Afm Probe Tip and Image Reconstruction from Noisy Measurements
Authors: Fischer H. , Nittmann J. 
Published: April 2011

AbstractWe have tested the application of a recently developed probe tip reconstruction method to AFM images from semiconductor surfaces. The method by Villarrubia is the first to enable the construction of a probe tip from the AFM measurements alone. Here is a summary on how this method can be implemented. Experience shows that for some real surface data, experimental noise prevents the reconstruction of realistic tips. Therefore we present some preliminary results of how noise reduction methods applied to the measurements can provide access to more realistic tip shapes which are the basis for a useful image reconstruction.
AFM Analysis of ECR Dry-Etched Ingap, Alinp and Algap
Authors: Ren F. , Hobson W. S. , Lothian J. R. , Lopata J. , Caballero J. A. , Lee J. W. , Pearton S. J. , Cole M. W. 
Published: April 2011

AbstractThe etch rates of InGaP, AlInP and AlGaP increases dramatically with microwave power in ECR BCl3- or CH4/H2-based discharges, reaching values near 1μm·min−1at 1000W, The surface morphologies of these materials however behave much differently as the microwave power is increased. For BCl3 etching of InGaP the surface RMS roughness decreases from 36nm at 250W to 2nm at 1000W. For AlInP, there is little change in surface morphology, whereas for the common binary component of these two materials, InP, the surface becomes very rough at high powers (>60nm RMS). By contrast, the morphologies of the three ternaries remain smooth over a wide range of conditions with CH4/H2/Ar. The AFM analysis, coupled with AES enables us to understand these different responses in terms of volatility of the respective chloride, metalorganic and hydride etch products.
Response Time For Optical Emission And Mass Spectrometric Signals During Etching Of Heterostructures
Authors: Thomas S. , Chen H. H. , Pang S. W. 
Published: April 2011

AbstractPlasma etching of III-V heterostructures has been monitored using optical emission spectroscopy and mass spectrometry. For the Ga optical emission signal at 417.2 nm, a response time as fast as 0.2 s has been measured. The response time of the mass spectrometer is limited by the transit time of etch products from the wafer surface to the ionizer. A minimum response time of 0.9 s was measured by reducing the signal integration time of the mass spectrometer. Saturation of the optical emission signal has been shown to be related to the residence time of etch gases by varying the flow rate or pressure. Decreasing residence time by reducing the pressure from 6 to 2 mTorr and maintaining a constant flow rate caused the Ga emission signal saturation time to decrease from 7 to 3 min. The 145ASC12+ signal saturated before the Ga emission signal at 417.2 nm. Endpoint detection for etching an AlInAs emitter and stopping on a GaInAs base was studied. By monitoring the changes in the Ga emission intensity, only 2 nm of the GaInAs base layer had been removed when the emitter etch was stopped.
Investigation of Passivation Effects in InP Hemt Layers
Authors: Hove M. Van , Finders J. , Zanden K. Van Der , Geurts J. , Rossum M. Van 
Published: April 2011

AbstractWe have investigated the influence of the deposition of a passivating silicon nitride layer on the electron transport in InAlAs/InGaAs/InAlAs quantum wells capped with a thin InGaAs layer. This structure is grown by Molecure Beam Epitaxy lattice-matched on InP substrates for the fabrication of High Electron Mobility Transistors. The InGaAs cap layer is added to reduce the ohmic contact resistance. In a first step to illuminate the complicated structural changes involved when passivating fully processed devices, we studied the influence of silicon nitride layer deposition on the virgin epilayers. The electrical transport properties were characterised by resistance, mobility, carrier concentration and magnetoresistance measurements, while Raman spectroscopy was used to probe the vibrational properties which are influenced by the free carriers. Because of the small penetration depth of the laser light mainly the lattice vibrations in the InGaAs ohmic contact layer were observed in the Raman spectra. Before passivation this thin highly doped cap layer is depleted, as confirmed by magnetoresistance measurements, that show a single conducting path in the two-dimensional electron gas formed in the InAlAs/InGaAs/InAlAs QW, and only bulk-like InGaAs phonons are observed in the cap layer. After passivation a shift to lower frequencies of the GaAs-like mode indicates a high electron concentration in the InGaAs cap. The results of the Raman analysis are in good agreement with the electrical transport data that show a considerably lower resistance after passivation. Magnetoresistance measurements on passivated layers confirmed the creation of an additional conducting path in the InGaAs cap layer introduced by the silicon nitride deposition process.
Optical And Mass Spectrometric Diagnostic Methods For Plasma Etching
Authors: Donnelly V. M. 
Published: April 2011

AbstractOptical emission and line-of-sight mass spectrometry were used to monitor Cl, Cl2 and SiClx reaction products during etching of Si(100) in a high density (1–2 × 1011 ions/cm3) chlorine plasma. Emission from atomic Cl, and from ion-pair states of C12 at 7.2 – 9.4 eV were monitored, along with emission from a small amount of Xe that was added to the gas to sense changes in the electron energy distribution (i.e. actinometry). In this manner, the normalized emissions provide a measure of relative number densities of C12 and Cl. These measurements were converted into absolute numbers by extending the measurements to extremely low powers, where C12 and Xe number densities are known. These results are compared with those recorded with a differentially pumped, line-of-sight mass spectrometer. At power densities of ˜0.5 W/cm3, the discharge is almost completely dissociated in the plasma source region (˜90%), while above the wafer and downstream of the plasma, the percent consumption of Cl2 drops to 75%. A long term upward drift in the percent dissociation in the source was observed, attributable to a time-dependent decrease in the rate of Cl-atom recombination on the glass walls. These results are compared with recent model predictions and are also discussed in terms of their significance for surface etching reactions, and real-time control.
Electron Density Effects in the Modulation Spectroscopy of Strained and Lattice-Matched InGaAs/InAlAs/InP HEMTs.
Authors: Dimoulas A. , Davidow J. , Giapis K. P. , Georgakilas A. , Halkias G. , Kornelios N. 
Published: April 2011

AbstractThe effects of the channel electron density on the interband optical transitions of strained (x = 0.6 and 0.65) and lattice-matched (x = 0.53) lnxGa1−xAs/In0.52Al0.48As/InP high electron mobility transistor structures have been investigated by phototransmittance at room temperature. Analysis of the ground and first excited transitions for low and high densities, respectively, enabled a separate estimation of the electron densities occupying each one of the first two subbands. It was found necessary to include the modulation of the phase-space filling in the analysis of the spectra, especially for the samples with a high electron density, in which case this mechanism becomes dominant.
Fabrication and Luminescence of Etched Quantum Rings and Vertically Coupled Dots
Authors: Philippa G. E. , Galeana J. A. Mejia , Cassou C. , Wang P. D. , Guasch C. , Vögele B. , Holland M. C. , Torres C. M. Sotomayor 
Published: April 2011

AbstractThe fabrication of GaAs-GaAIAs coupled quantum dots and of quantum rings using electron beam lithography and dry etching is described. Coupled dots of physical diameter of 500 and 250 nm were fabricated and processed with top electrical contacts to apply an electric field. We show that the emission spectrum of coupled dots is modified by the electric field. Quantum rings of 400 nm outer diameter and wall thickness of 25 nm were fabricated. The emission spectrum from rings showed the quantum well emission shifted to higher energies and although its intensity decreased by about one order of magnitude there was little linewidth broadening.
In-Situ and Ex-Situ Studies of Silicon Interfaces and Nanostructures by Ellipsometry and Rds
Authors: Rossowl U. , Mantese L. , Frotscher U. , Aspnes D. E. , Richter W. 
Published: April 2011

AbstractWe report surface-induced optical anisotropy (SIOA) spectra and dielectric function data of vicinal Si(001) surfaces using reflectance-difference spectroscopy (RDS) and spectroscopic ellipsometry (SE). To find the main contributions of the optical response we took data for clean and by hydrogen, oxygen, and arsenic modified surfaces. The SIOA lineshapes, as measured by reflectance-difference (RD) spectroscopy, can be either derivative-like or similar to the dielectric function as measured by SE. The derivative-like spectra appear to be associated with step contributions while the dielectric-function-like behavior appears to arise from terrace dimers and/or changes in chemical species bonded to the steps. In addition, we present SE data of silicon nanostructures formed by electrochemical etching and find that their behavior is dominated by interface properties.
Scanning Electron Microscopy (Sem), Transmission Electron Microscopy (Tem) and Secondary Ion Mass Spectroscopy (Sims) Characterization of the Morphology of Aluminum Bond Pads for Surface Reflectivity Applications.
Authors: Schade M. , Ai R. , Stein Y. , Anderson T. 
Published: April 2011

AbstractExtreme variations in surface reflectivity/topography have been observed on silicon wafers with evaporated aluminum metallization following thermal annealing processes. Such topographic variations negatively impacted the performance of wire bonder pattern recognition systems. It was proposed that this variation was attributed to differences in deposition rates during evaporation of the aluminum front metallization. SEM analysis revealed that the topographically rough sites, deemed as normal for this processing sequence, had large numbers of hillocks, while the smooth sites exhibited limited numbers of hillocks after heat treatment. SIMS depth profiling analyses did not indicate that any elemental difference existed between the smooth and the rough sites, although interfacial differences were detected. Specifically, the Al-Si interface for the rough surface was more graded in nature while the Al-Si interface for the smooth surface was more abrupt. TEM analysis of the rough sites revealed that a three-dimensional island growth mechanism prevailed during film growth, resulting in uneven surface development, whereas analysis of the smooth sites showed a columnar grain structure.
Obic Modelling, Numerical Computation and Measurement of Silicon Parameters in The Presence of Defects
Authors: Barbero F. , Maggio G. M. , Moore R. A. 
Published: April 2011

AbstractIn recent years the use of non-destructive techniques involving the generation of minority carriers by means of an electron beam (EBIC) or a LASER beam (OBIC) have proven to be useful in the study of the electrical properties of process-induced defects in bulk silicon. The development of a model and algorithm to obtain the diffusion length L, the surface recombination ratio S and the defect-increased recombination, by collecting the LASER-Beam-Induced-Current scanning the sample using a Schottky diode is presented. First a model to obtain the probability of collection of an electron-hole-pair generated by a point source is derived. The finite size of the collecting junction, L and S make the solution of the diffusion equation available only in integral form; it is therefore necessary to perform a numerical integration. Then a least-squares algorithm for identifying L and S in the case of bulk silicon without defects is obtained. Lastly the effect of a finite size generation volume and the increased recombination due to a line defect is taken into account. The effect of S and the distance of the defect from the surface on the signal contrast is analysed. This determines the information depth of the collected signal. It is shown how a high value of surface recombination ratio reduces the contrast and therefore impairs the possibility of detecting low-strength defects.An analysis of the experimental results is performed and they are found to be in good agreement with the model.
Structural Characterization of Reactive Ion Etched Semiconductor Nanostructures Using X-Ray Reciprocal Space Mapping
Authors: Bauer G. , Darhuber A. A. , Holy V. 
Published: April 2011

AbstractWe have studied GaAs/AlAs periodic quantum dot arrays using high resolution x-ray diffraction (reciprocal space mapping) around the (004) and (113) reciprocal lattice points. From the distribution of the diffracted intensities we deduced the average strain status of the dots. From the numerical simulations it is evident that random elastic strain fields are present, which extend through almost the entire volume of the quantum dot. The simulations of the x-ray measurements revealed that the crystalline part of the dots is considerably smaller as scanning electron micrographs would indicate.
Dopant Quantification By X-Ray Absorption Spectroscopy: Zn IN InP
Authors: Niu L. , Karlicek R. F. , Geva M. , Citrin P. H. 
Published: April 2011

AbstractX-ray absorption spectroscopy has been applied to layered Zn-doped InP structures containing systematically varying amounts of Zn spanning a factor of -40. The structures, similar to those used in optoelectronic laser devices, were characterized with x-ray absorption spectroscopy and SIMS to determine quantitatively the Zn concentrations. In addition to being non-destructive, the former technique was shown to be substantially more precise. A well-defined concentration regime is established in which substitutionally occupied Zn is directly proportional to Zn exposure during growth.
The Uniformity Of Surface Passivation After (NH 4)2S Treatment Studied By Near-Field Scanning Optical Microscopy
Authors: Liu Jutong , Kuech T. F. 
Published: April 2011

AbstractWe have achieved spatially resolved room temperature photoluminescence (PL) from MOVPE GaAs (001) surfaces by Near-Field Scanning Optical Microscopy (NSOM). The PL intensity variation was related to the change of surface state density. Using this technique, the uniformity of surface passivation after (NH 4)2S treatment has been studied. We have performed the topography, reflection and PL measurements by NSOM as well as the topography measurements by Atomic Force Microscopy (AFM) on the as grown, etched and sulfur passivated GaAs samples. The uniformity of GaAs with a thin Al0.65Ga0.35As cap layer has also been studied and compared with the (NH 4)2S treatment. We found the sub-micron scale variations in PL intensity which were not correlated to the topographic features. Theoretical modeling has been used to obtain semi-quantitative analysis of the experimental results.
A New Method For The Electronic And Chemical Passivation Of GaAs Surfaces Using CS2
Authors: Lee Ju-Hyung , Xu Yanzhen , Burrows Veronica A. , McMillan Paul F. 
Published: April 2011

AbstractA new GaAs surface passivation method, CS2 treatment at moderate temperature was developed for effective passivation of GaAs surfaces. The CS2 treatment of GaAs surfaces at 350°C and 10 atm leads to deposition of a homogeneous film, with a thickness of several hundred Å. The passivation layer thus produced causes a significant enhancement in room temperature photoluminescence intensity and the passivation effect of the sulfide film was confirmed by Raman spectroscopy. The passivation layer remained electrically and chemically stable over a period of nine months under ambient atmospheric conditions. In-depth Auger electron spectroscopy (AES) revealed that the carbon and oxygen content in the film was negligible, whereas sulfur was uniformly distributed throughout the film. A metal-insulator-semiconductor diode whose insulating layer is produced by the CS2 treatment shows well-defined accumulation and depletion regions in its capacitance-voltage (CV) characteristics with low hysteresis.
Cathodoluminescence Spectroscopy For Evaluation Of Defect Passivation In GaSb
Authors: Pal U. , Piqueras J. , Dutta P. S. , Bhat H. L. , Dubey G. C. , Kumar Vikram , Dieguez E. 
Published: April 2011

AbstractCathodoluminescence (CL) technique has been employed to study the optical properties of GaSb after deposition of hydrogenated amorphous silicon (a-Si:H). CL images recorded at various depths in the samples clearly show passivation of extended defects on the surface as well as in the bulk region. The passivation of various recombination centres in the bulk is attributed to formation of hydrogen-impurity complexes by diffusion of hydrogen ions from the plasma. Enhancement in luminescence intensity is seen due to passivation of non-radiative recombination centres. The passivation efficiency is found to improve with increase in a-Si:H deposition temperature.
Cathodoluminescence Study Of Diffusion Length And Surface Recombination Velocity In III-V Multiple Quantum Well Structures
Authors: Chao L.- L. , Freiler M. B. , Levy M. , Lin J.-L. , Cargill G. S. , Osgood R. M. , McLANE G. F. 
Published: April 2011

AbstractWe describe studies of luminescence and lateral transport properties of excited carriers in GaAs- A1GaAs multiple quantum well (MQW) structures by cathodoluminescence measurements in a scanning electron microscope. We examine the effect of in-plane, etch-defined feature size on MQW luminescence efficiency and variability, and determine the diffusion length and its temperature dependence from ˜ 8K to 250K. Our measurements also provide information about nonradiative surface recombination velocity at the side walls of etch-defined MQW structures.
Raman Spectroscopic Study Of Ion-Implanted And Annealed Silicon.
Authors: Tuschel David. D. , Lavine James P. , Russell Jeffrey B. 
Published: April 2011

AbstractRaman spectroscopy is used to characterize silicon implanted with arsenic and then annealed. The implant dose ranged from 2 × 1012 to 2 × 1013/cm2. The as-implanted samples show a decreased Raman intensity of the 520 cm−1 optical mode, and increased Raman intensity between 400 and 500 cm−1 with respect to an unimplanted silicon wafer. The higher arsenic doses show an increase in the second-order transverse acoustic-mode (TA) intensity around 300 cm−1 relative to the secondorder transverse optical-mode (TO) intensity near 970 cm−1. Annealing restores the 2TA/2TO relative intensities and sharpens the weak peaks between 600 and 900 cm−1. The Raman spectrum is altered by the lowest dose implant and the annealing steps do not lead to a complete recovery of the pre-implant Raman spectrum. This permits the monitoring of lowdose ion-implant damage recovery with Raman spectroscopy.