bluuebunny/crossref_metadata_2025 huggingface dataset:
Synchrotron Radiation Studies of Magnetic Materials
Authors: Erskine J. L. , Ballentine C. A. , Araya-Pochet Jose , Fink Richard
Published: March 2011

New opportunities for research on magnetic materials are emerging as a result of quiet revolutions in several areas including: materials synthesis techniques, surface characterization capabilities, new magnetic sensitive detectors and spectroscopic techniques, improved synchrotron radiation instrumentation, and predictive modeling based on first principals calculations. This paper describes some of the more recent advances and assesses some of the new opportunities that are emerging in the field of magnetic materials research.
Reflectance-Difference Spectroscopy: a New Real-Time, In-Situ Analysis of MBE and OMCVD Growth Surfaces.
Authors: Colas E. , Aspnes D.E. , Bhat R. , Studna A.A. , Koza M.A. , Keramidas V.G.
Published: March 2011

Reflectance-difference spectroscopy (RDS) is a recently developed optical technique that allows to monitor chemical and structural changes at a growing semiconductor surface, in-situ and in real-time. This technique was applied recently to organometallic chemical vapor deposition (OMCVD) on a [100] GaAs growth surface. The results show that submonolayer coverage of reacted species can be followed by this technique, which provided unique insights into the microscopic growth mechanisms. The time, temperature and pressure dependences of surface coverage show that OMCVD growth is controlled by two basic processes with distinct activation energies, i.e. reversible chemisorption (at -26 kcal/mole), and decomposition (at 39 kcal/mole) of trimethylgallium (TMG) at surface lattice sites. The importance of reversible chemisorption, which is of an excluded-volume type, due to the large size of the TMG molecule, had been overlooked until now in the literature, where only one activation energy was used to describe growth kinetics.
Vertical Bridgman Growth of GaAs
Authors: Kremer R. E. , Francomano D. , Beckhart G. H. , Burke K. M. , Miller T.
Published: March 2011

We have developed a process to grow both undoped, semi-insulating (SI) and silicon-doped, semiconducting (SC) GaAs using a vertical Bridgman method. The technique combines advantages of both liquid encapsulated Czochralski (LEC) and horizontal Bridgman (HB) processes. SI ingots, grown in pBN boats, and SC ingots, grown in quartz boats, are passed through a relatively shallow temperature gradient. Properties of the resulting material are highly uniform across the surface of a wafer. Because of the small temperature gradient, dislocation densities are very low (typically under 4000/cm∩2).
Rapid Thermal Annealing of GaAs/AlGaAs Coupled Double Quantum Wells
Authors: Koteles Emil S. , Elman B. , Armiento C. A. , Melman P. , Chi J. Y. , Holmstrom R. J. , Powers J. , Owens D. , Charbonneau S. , Thewalt M. L. W.
Published: March 2011

The effect of rapid thermal annealing (RTA) on the shapes of silicon dioxide capped symmetric coupled double GaAs/AlGaAs quantum wells (CDQW) has been investigated. In contrast to previous results on single quantum wells in which increases in exciton energies were observed after RTA, large decreases in exciton energies were seen in CDQWs. Furthermore, there was clear evidence, in the excitation spectrum and in increases in the lowest energy exciton lifetime, of asymmetry present in the heterostructure after RTA.
Local Atomic Interdiffusion in CdTe/HgCdTe Multilayered Structures
Authors: Kim Y. , Ourmazd A. , Feldman R. D. , Rentschler J. A. , Taylor D. W. , Austin R. F.
Published: March 2011

We combine chemical lattice imaging with digital pattern recognition to study atomic interdiffusion at individual CdTe/HgCdTe interfaces in multi-quantum well structures. In this way we obtain quantitative composition profiles for “as grown” samples, and investigate their development as a function of annealing temperature. Our results indicate that interdiffusion depends on the position of the quantum well with respect to the surface, beginning first at quantum wells close to the surface, and proceeding towards the substrate. Our approach allows the quantification of interdiffusion as a function of time, temperature, and distance from the surface. The implications of these results for the stability of CdTe/HgCdTe structures, and the interpretation of X-ray data are discussed.
Phase Separation and Atomic Ordering in Epitaxial Layers of III-V Compound Semiconductors
Authors: Mahajan S. , Shahid M. A.
Published: March 2011

MIcrostructural characteristics of phase separated and ordered ternary and quaternary layers of Ill-V compound semiconductors grown by a variety of techniques are highlighted. It is argued that the fine scale contrast modulations seen in a number of layers arise from a two-dimensional, surface spinodal decomposition at the growth temperature. On the other hand, coarse contrast modulations could result from accommodation of asymmetrical strains associated with the twodimensional decomposition.

Long range atomic order is observed in a variety of layers grown by different techniques and co-exists with phase separation. In InGaAs and InGaAsP layers, grown on (001) InP substrates, ordering is observed only on the two {111} planes that contain the line of intersection of the {111}in plane with the (001) InP surface. As a result of ordering, periodicity along the 〈111〉 direction is doubled. Also, the influence of growth temperatures and growth rates on ordering characteristics in GalnP and (Ga, Al) InP layers is reported.
Inversion Domain Boundary Dislocations in Heteroepitaxial Films
Authors: Cheng T. T. , Pirouz P. , Ernst F.
Published: March 2011

Transmission electron microscope (TEM) images of inversion domain boundaries (IDB) show fringe contrast, thus indicating a relative displacement between the two adjoining domains. When the IDBs are facetted, different facets may have different displacement fault vectors. This implies that when the facetting changes from one plane to another, there should be a dislocation at the intersection of the planes. This is termed an “inversion domain boundary dislocation” and it will have a Burgers vector b=R1–R2 where R1, and R2 are the fault vectors of the two facets. Experimental results for facetted IDBs and IDB dislocations in SiC grown heteroepitaxially on (001) silicon are presented.
I-V, C-V, and Hall Effect Studies of Indium-Doped Lpe GaAs
Authors: Chen J.F. , Xie K. , Wie C.R.
Published: March 2011

We have studied the effects of In doping on the electrical properties of a liquid phase epitaxially (LPE) grown GaAs. The I–V characteristics of Au-GaAs Schottky diodes show, for the layer with In concentration of 2.4 × 1019 cm−3, an ideality factor close to 1.04 over more than seven decades of current. For the same sample, the reverse I–V characteristics are close to an ideal Schottky diode and can be fitted by a theoretical curve, combining the thermionic field emission and thermionic emission. The electrical improvement is closely related to the low etch pit density and other structural improvements. This indicates that, as in the LEC growth, In has effects on the reduction of disloation density in the LPE grown GaAs epi-layer. For doping levels higher than 6×1019 cm−3, an excess forward current is produced at low voltages and low temperatures. A large leakage current is observed under the reverse bias. This property is attributed to a high field effect, with field emission via a trap state as the most likely cause. Hall measurements showed that the ratio of free-carrier concentration ND−NA to the total-carrier concentration ND+NA increased with increasing In concentration.
GaAs on Si Grown by Mbe: Progress and Applications for Selectivity Doped Heterojunction Transistors (SDHTs)
Authors: Chand Naresh , Van Der Ziel J. P. , Weiner J. S. , Sergent A. M. , Lang D. V.
Published: March 2011

Recent progress of GaAs-on-Si technology is reviewed and the importance of initial nucleation is emphasized. Growth initiation with a Ga prelayer at a suitable low temperature combined with migration enhanced epitaxy and in-situ thermal annealing has a prospect of giving substantially improved material quality. During the initial growth, use of the minimum necessary As4/Ga flux ratio is found to be critical. The random alignment of the major axis of the oval defects is suggested to be an alternative simple technique to detect the presence of antiphase domains. Patterned growth or post growth patterning releases tensile stress only if the growth edges are free. GaAs-on-Si was completely relaxed from stress by post-growth patterning to 5 μm × 5 μm size patterns. Steps on the surface due to substrate misorientation do not affect the two dimensional electron gas (2DEG) transport properties in AlGaAs/GaAs selectively doped heterojunction transistor (SDHT) structures. For a sheet density of 1012 cm−2, the 2DEG mobility >50,000 cm2V−1s−1 at 77 K was obtained on Si substrates, which is sufficient for fabrication of high performance SDHTs. The study shows that GaAs-on-Si has a great potential for SDHT technology.
Formation of High Quality GaAs/Si Hetero-Structure by Solid Phase Epitaxy
Authors: Miyao M. , Shimada T. , Nishid A. , Inada T. , Tamura M. , Ishino M. , ohbu I.
Published: March 2011

Improvements of crystal quality in GaAs/Si heterostructure by solid phase epitaxy (SPE) are described. RBS and TEM measurements indicate that high density defects are located near the GaAs/Si interface after “2-step MBE”. Utilization of post SPE process (amorphization plus regrowth) significantly improve crystal qujali ty at the GaAs/Si interface, although a small stress field is introduced. In addition a new relation between photoluminecence intensity ratio and stress field is established. This provides a useful too] for measuring small stresses remaining in the GaAs/Si hetero-structure.
Thermal Annealing Effects in the Strained (Ga, In) as Layer
Authors: Choi Y-W. , Kim H.M. , Rajeswaran G. , Wie R.
Published: March 2011

We have studied the ternary (Ga, In)As layers in GaInAs/GaAs heterostructure systems after conventional furnace annealing or rapid thermal annealing (RTA). Measurement was done by the double crystal X-ray rocking curve technique (XRC) and the Auger Electron Spectroscopy technique (AES). X-ray rocking curves show an asymmetric shoulder in the GaInAs epilayer peak indicating a smaller lattice spacing near the surface. Epilayer peaks of encapsulated samples also show an asymmetric shoulder which is perhaps due to the tensile stress in the epilayer caused by the encapsulant film. AES depth profiles for 600°C, 15 minutes proximity annealed sample show that the concentrations of Ga, In, and As are not uniform over about 60 nm depth, showing a Garich and In, As-deficient surface. For 700°C, 20 seconds a RTA treated sample shows no such non-uniformity.
The Influence of the Arsine Source on the Purity of InGaAs Grown by Hydride VPE
Authors: Noel Buckley D. , Matthiesen M. M.
Published: March 2011

The relatively high background carrier concentration obtained in unintentionally doped epitaxial layers of III-V materials imposes a limitation on applications of the hydride VPE process. It is usually attributed to impurities in the gas sources. Results are presented for InGaAs grown by hydride VPE using a range of growth conditions. Carrier concentrations and growth rates for the various samples were determined using, respectively, Polaron electrochemical profiler measurements and scanning electron microscopy. It is shown that the observed background carrier concentration increased with increasing input mole fraction of arsine under conditions of constant growth rate. This strongly implicates the arsine feed gas as a predominant source of impurity. Attempts to purify the arsine feed gas using sodium alumina-silicate molecular sieves are described. Polaron electrochemical profiler measurements and Hall effect measurements on samples grown both with and without molecular sieves in the arsine feed line are presented. From a comparison of the corresponding values of carrier concentration and mobility it is shown that Type 4A molecular sieves were not effective in removing dopant impurities from the 4% arsine-hydrogen mixture used.
Ion Implantation and Characterization of III-V Materials
Authors: Wilson R. G. , Rensch D. B.
Published: March 2011

We have implanted most dopant elements into GaAs, GaP, InP, and InSb, to energies from 10 to 700 keV, and a few up to 2.4 MeV, in random and channeled orientation, annealed some of these implants, and measured the depth distributions using secondary ion mass spectrometry (SIMS) . We have calculated values of Rm, Rp, ΔRp, γ1, β2, using an LSS formulation, and measured these same profile parameters for the experimental profiles using a Pearson IV computer fitting routine. We describe a study of the fabrication of self-aligned W-gate FETs in GaAs using Si-implanted channels and source/drains, and a buried p implant (Be or Mg) to compensate the backside (tail) of the Si profile. The implant profiles and electrical device characteristics, including the effects on AVt of various implant conditions, are discussed.
Ion Implantation Damage and its Annealing Characteristics in an AlAs/GaAs Layer Structure
Authors: Cullis A. G. , Jacobson D. C. , Poate J. M. , Chew N. G. , Whitehouse C. R. , Pearton S. J.
Published: March 2011

The implantation of Ar+ ions into AlAs/GaAs layered samples is shown to give very different damage structures in the two materials. While the GaAs is relatively easily amorphised, the AlAs is quite resistant to damage accumulation and remains crystalline for the ion doses employed in these investigations. The behaviour of the different damage structures when subjected to rapid thermal annealing treatments is described in some detail. It is demonstrated that differences in the initial damage state have a strong influence upon the nature of lattice defects produced by annealing.
Some Applications of Ion Beams in III-V Compound Semiconductor Device Fabrication
Authors: Donnelly J. P. , Anderson K. K. , Woodhouse J. D. , Goodhue W. D. , Yap D. , Gaidis M. C. , Wang C. A.
Published: March 2011

Ion-beam-assisted etching of GaAs/AlGaAs and InP/GaInAsP, ion-beam disordering of GaAs/AlGaAs multiple-quantum-well structures, and ion implantation in InP are discussed.
Mg+ Ion Implantation into GaAs : Annealing and Photoluminescence Properties
Authors: Takeuci Yoshinori , Makita Yunosuke , Mori Masahiko , Ohnishi Nobukazu , Shibata Hajime , Matsumori Tokue
Published: March 2011

Mg ion-implantation was carried out into very pure GaAs made by molecular beam epitaxy, in which the dose of Mg atoms, [Mg] was varied from l×1015 to 1×1020 cm−3 . As a method of characterization, low temperature photoluminescence (PL) studies were carried out as a function of [Mg]. A new emission, denoted by [g-g] was observed between bound exciton emissions and the emission due to 1 and-to-acceptor pairs. It was found that [g-g] appears around [Mg]= 2×1016 cm−3 and becomes a dominant emission at [Mg] over l×1017 cm−3. A significant shift of [g-g] towards the lower energy side with increasing [Mg] was reproducibly obtained and its PL properties were carefully investigated in terms of annealing temperature, TA and excitation density. Results revealed that the implanted Mg atoms become optically active at TA over 600 [g-g] was suggested to be acceptor-acceptor pair, which is consistent with the theoretical explanation that its radiative mechanisms is ascribed to the pair between excited-state acceptors. The systematic energy shift inherent to [g-g] was attributed to the growing ionization energy of the pair with increasing pair distance.
Electrical Activation Behavior of Ion Implanted Silicon in Gallium Arsenide During Rapid Thermal Annealing
Authors: de Souza J.P. , Sadana D.K. , Hovel H.J.
Published: March 2011

Rapid thermal annealing (RTA) (800–1000°C, 1–60 s) was performed on capless and silicon nitride (SixNy) capped GaAs samples implanted with Si (30 keV, 4.5×1013cm−2 ) and SiF+ (50 keV, 4.5×1013cm−2 ). The maximum activation for the Si+ implants saturated at 25% (capless) and 42% (capped) and that for the SiF+ implants saturated at 20% (capless) and 35% (capped). The activation degraded at temperatures > 825°C due to surface decomposition in the capless annealing case and at > 925°C due to the cap failure in the capped annealing case. For all the RTA conditions studied here, higher activation always occurred with the Si+ rather SiF+ implants. An activation energy of 0.48 eV for the annealing process was determined from the electrical data. It was also observed that the heating and/or cooling rates can significantly influence the electrical activation.
Reactive Ion Etching of Indium-Based III-V Materials using CH4-H2-Ar Mixtures
Authors: Fathimulla A. , Loughran T. , Bates J.
Published: March 2011

Dry etching of indium-based III–V materials in chlorine-based gases is difficult because of the low vapor pressure of the indium chloride by-product. Recently, reactive ion etching of InP(1,2), and GaAs(3,4) using methane, hydrogen and argon mixture in which volatile organometallic group III compounds are formed has been employed. In this paper, we report the reactive ion etching of indium-based materials using CH4:H2:Ar and SiCl4:Ar mixtures.
Evolution of the GaAs(001) Surface Physico-Chemical Characteristics and Electrical Properties of the Si3N4/GaAs Interface with the NH3Photolysis Treatment of the GaAs Surface.
Authors: Guizot J.L. , Alnot P. , Perrin J. , Allain B.
Published: March 2011

Cleaning treatments of GaAs(001) by UV decomposition of NH3 has been studied by means of X-ray photoemission spectroscopy (XPS) and X-ray photoelectron diffraction (XPD). This photolysis treatment is shown to decompose the surperficial oxides and to remove the carbon of contamination. The surface cleaning is followed by the formation of gallium nitride overlayers. When used prior to UVCVD silicon nitride deposition, this treatment is shown to improve the electrical characteristics of the Si3N4/GaAs MIS structure.
Downstream Plasma Activated Etching of IIIV Compound Semiconductorsa
Authors: Iyer R. , Lile D.L.
Published: March 2011

We have demonstrated a novel downstream plasma activated vapor phase etching of III-V compound semiconductors using ethylene di bromide as the etchant. Highly reproducible surfaces and etch rates were obtained by monitoring the reaction process with a mass spectrometer. Etch rates on InP of up to 4500Å/min, at temperatures as low as 160°C, at an rf power input of 25 watts were achieved with no evident damage to the surface as indicated by PL measurements. Apparent activation energy measurements seem to suggest that the etch products might be organometallic in nature, in contrast to inorganic etch products seen in most etching studies. Etching is partially anisotropic and resulted in smoother surfaces when H2 was used as the carrier gas for the etchant instead of N2.
Thin-Film Encapsulants for Thermal Processing of GaAs
Authors: Molarius J.M. , Kolawa E. , Morishitaal K. , Pan E.T-S. , Tandon J.L. , Nicolet M-A.
Published: March 2011

During heat treatment of GaAs there is a tendency for arsenic to evaporate. This process can have deleterious consequences and must be controlled during the annealing of GaAs by using encapsulants. In this work we use a Cr collector to catch the evaporated atoms. This collector is placed on top of GaAs or GaAs/cap during annealing. We survey the effectiveness of W, Hf and HfN as capping materials for thermal annealings of 10 min. for 450–700 C and compare them to Si3N4. The backscattering spectrometry results show that Si3N4 and W were excellent caps up to 700 C for 10 min. No evaporation was defected through HfN either, but hillock formation was detected on the surface. Hf failed because of its chemical reaction with GaAs at 650 C, 10 min.
A Comparative Study of Te- and Ge-Based OHMIC Contacts on GaAs
Authors: Wuyts K. , Vantomme A. , Silverans R.E. , Van Hove M. , Van Rossj M.
Published: March 2011

The formation of furnace processed Te- and Ge-based ohmic contacts on n-GaAs was investigated using Rutherford Backscattering Spectroscopy and electrical measurements. Contact resistivities obtained with the Ni/Au/Te metallization were comparable to those of the standard Ni/AuGe scheme, the lowest value for both metallizations being 5.10−6Qcm2. The onset of ohmicity of the Au/Te scheme varied from 480°C to 550°C by changing the Au/Te thickness ratio. The diffusion characteristics of the contacting metals were studied on GaAs as well as on SiO2 substrates. Arguments in favor of the model explaining the nature of the contacts by the formation of a heterojunction-like structure are adduced.
Organometallic Vapor Phase Epitaxial Growth of ZnGeAs2 and (ZnGeAs2)xGe1−x on GaAs
Authors: Solomon G. S. , Posthill J. B. , Timmons M. L.
Published: March 2011

Epitaxial single crystal (001) chalcopyrite-structure ZnGeAs2 and single crystal (100) zinc blende-structure (ZnGeAs2)xGe1−x alloys have been grown by organometallic vapor phase epitaxy on (100) GaAs. Selected area electron diffraction was used to determine the crystal structure for several Zn:Ge molar flow ratios. Bulk chemical composition was determined by electron microprobe and correlated to crystal lattice constants obtained from x-ray diffraction. Due to the lattice mismatch between chalcopyrite-structure ZnGeAs2 and the GaAs substrate, the epitaxy is elastically strained, compressing the a-lattice constant and elongating the c-lattice constant. Optical absorption and transmission spectroscopy indicate the zinc-blende-structure material has an indirect band gap of approximately 0.6 eV, whereas the chalcopyrite ZnGeAs2 has a direct band gap of 1.15 eV. Secondary ion mass spectroscopy reveals significant Zn diffusion into the GaAs substrate if the Zn:Ge molar flow ratio exceeds the ratio required for stoichiometric chalcopyrite-structure crystal growth.
Measurement of Mobility Profile in GaAs MESFET's by Schottky Barrier Technique with Gate Current Correction
Authors: Qi Xiang , Lichun Wang , Jinsheng Luo
Published: March 2011

The mobility profile of electrons in active layer of GaAs MESFET has an inportant effect on the device performance. The mobilities at layers of different depth can be measured by changing the negative gate bias, but the electron mobility near the surface can't be measured yet due to the depletion of electrons in the surface layer. This paper introduces a differential d.c. equivalent model, in which the Schottky barrier can be forward biased and the gate current correction is properly included. Applying this model, we can precisely calculate the drift and gecmetrical magnetic resistance mobilities very close to the surface layer.
Sheet Density and Well Thickness Effects on Photoluminescence from Pseudomorphic HEMT Structures
Authors: Colvard C. , Nouri N. , Lee H. , Ackley D.
Published: March 2011

Low temperature photoluminescence was studied in a large number of pseudomorphic HEMT's having an InxGa1−xAs quantum well. The spectra show strong qualitative differences when the Fermi level is above or below the second conduction subband, and in the latter case they are power dependent. A slight enhancement is seen at the Fermi edge only when it lies close to the higher subband. Excellent agreement is found between the measured Fermi energy and the two-dimensional carrier density in the well.
A Mathematical Model of the Gas-Phase and Surface Chemistry in GaAs Mocvd
Authors: Coltrin Michael E. , Kee Robert J.
Published: March 2011

This paper presents a detailed mathematical model of the coupled gas-phase chem- istry, surface chemistry, and fluid mechanics in the MOCVD of GaAs from trimethylgallium and arsine in a rotating-disk reactor. The model predicts steady-state deposition rates as a function of susceptor temperature and partial pressure of the reactants. Rate constants in the model have been adjusted to match experimental deposition rates from the literature.
Highly Strained InAsxPl-X/InP Quantum wells Prepared by Flow Modulation Epitaxy
Authors: Schneider R. P. , Wessels B. W.
Published: March 2011

Flow modulation techniques have been used to prepare highly strained InAsxPl-x/InP quantum well structures in an atmospheric pressure organometallic vapor phase epitaxial reactor. The compositions of the pseudomorphic wells ranged from x=0.40 to 0.74, corresponding to biaxial compressive strains of 1.3-2.4%. Well thicknesses ranged from 2 to 26 monolayers. The flow modulation growth conditions were found to have a strong influence on interface formation in the wells. For wells grown under optimized modulation conditions, low-temperature photoluminescence spectra revealed peak-splitting of the emission from the thinnest wells. This splitting is attributed to emission from regions in the wells with atomically smooth interfaces over areas greater in lateral extent than the exciton diameter. The full-width at half-maximum of the peaks is in the 6-15 meV range, comparable to the best reported values for lattice- matched InGaAs(P)/InP quantum wells grown by any technique, and is independent of well thickness or composition.
The Role of Arsine in Reducing Carbon in Triethylarsenic Grown GaAs Films
Authors: Speckman D.M. , Wendt J.P.
Published: March 2011

Very high carbon impurity levels (1018-1021cm−3) in GaAs films grown using triethylarsenic (Et3As) and trimethylgallium (Me3Ga) can be dramatically reduced by substituting a portion of the Et3As reagent with arsine during growth. Gallium arsenide epilayers grown at a deposition temperature of 560°C, a total V/III ratio =10, and the Group V reagent consisting of a mixture of Et3As and arsine, were found to exhibit carbon levels of only 5-7×1015cm−3for Group V mixtures ranging from 0-65% Et3As. All of these films were n-type, except for those grown using 100% arsine, which were p-type. The reduction in carbon incorporation in films grown using Et3As and arsine as co-reagents is shown to result from a unique, synergistic, reaction chemistry involving the two arsenic reagents. In particular, the decomposition of arsine to provide carbon-free, active arsenic fragments for growth is greatly enhanced by the presence of Et3As as a co-reactant.
Metalorganic Chemical Vapor Deposition of High Quality GaAs and AlGaAs Using Tertiarybutylarsine
Authors: Haacke G. , Watkins S. P. , Burkhard H. , Calbick C. J. , Quick J.
Published: March 2011

This paper discusses recent improvements achieved in the growth of epitaxial layers of GaAs and AlGaAs using the liquid arsine substitute tertiarybutylarsine (TBA) and metal alkyls. The high purity TBA now available yields undoped GaAs with residual donor/acceptor concentrations in the low 1014 cm−3 range. Under optimized growth conditiorp the layers are either n-type and have 77*K mobilities up to 85,000 cm2 //Vs or they are compensated or p-type. For aluminum gallium arsenide, layers grown with TBA have properties similar to arsine-grown material as demonstrated by low temperature photoluminescence (PL). The PL efficiencies and line widths of the TBA-grown AlGaAs samples are comparable to those prepared with arsine.
Low Pressure Growth of GaAs/AlGaAs Layers on 2N and 3N Substrates in a Multiwafer Reactor
Authors: Heyen M. , Heuken M. , Strauch G. , Schmitz D. , Jurgensen H. , Heime K.
Published: March 2011

The epitaxial growth of GaAs/AIGaAs layers and multilayer structures has been investigated in different low pressure horizontal multiwafer reactors for high throughput capable to handle several 2“ and 3“ wafers in one run. The growth behavior in these reactors will be described with respect to gas flow dynamics. The background carrier concentration is in the 1014 cm−3range. The uptake of dopants (SiH4) is strongly reduced upon pressure reduction.

The uniformity of GaAs and AIGaAs layer thickness is better than ±3 % over 3“ diameter substrates. The uniformity of composition (measurer on HEMT structures) is better than ± 1 % across 98 % of the wafer areas (± 0.5 % across 75 %). Also the reproducibility is better than 1 %. Results on the uniformity of dopant distribution will also be presented.

HEMT structures grown at low pressure conditions show mobilities of 100,000 cm2/Vs at 77 K and over 210,000 cm2/Vs at 20 K (ns= 6×1011 cm−2, spacer thickness 9 nm). HEMT devices with transconductance of 330 mS/mm could be achieved.
Vacuum Chemical Epitaxy: High Throughput GaAs Epitaxy Without Arsine
Authors: Fraas L. M. , Girard G. R. , Sundaram V. S. , Master Chris , Stall Rick
Published: March 2011

Metal organic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE) are well established methods for growing epitaxial GaAs and AlGaAs films. However, MOCVD equip- ment uses the highly toxic gas, arsine, and MBE equipment is very costly and coats only one wafer at a time. We have developed a vacuum chemical epitaxy (VCE) reactor which avoids the use of arsine and allows multiple wafers to be coated in a production environment.
The Growth, Characterization and Electronic Device Applications of GaAs/Si
Authors: Jordan A. S. , Pearton S. J. , Hobson W. S.
Published: March 2011

We review the growth of GaAs on Si by MO-CVD and MBE and discuss the relative merits of these techniques. Major emphasis is placed on the structural and optical characterization of the material that may be indicative of device performance. Typical GaAs layers on Si are free of anti- phase domains and the crystallinity at the surface for a 3-4μm thick deposit approaches that of bulk GaAs, as evidenced by the RBS backscattering yields and Si ion implantation profiles. The major drawbacks of GaAs heteroepitaxy on Si are the very large dislocation densities (106- 109cm−2), the relatively high unintentional doping concentration (>5 × 1014cm−3) that is partly attributable to Si outdiffusion, and the excessive bowing due to thermal expansion coefficient mismatch. While there are growth and processing techniques to overcome bowing or at least its influence, dislocations and low resistivity are hard to remedy. We discuss novel schemes to reduce dislocations (selective area growth, superlattices and thermal cycling) and efforts to improve the electrical properties (doping, optimization of V/III ratio). A variety of electronic devices and circuits have been fabricated using GaAs/Si. We shall present results on MESFETs, HBTs and HFETs processed in our laboratory and elsewhere. It is quite encouraging that HFETs with a transconductance of 220mS/mm are achievable. However, lasers in room temperature CW operation still have a very limited lifetime. Finally, we discuss the implications of GaAs/Si for a broader area of mismatched heteroepitaxy (InP/Si, InP/GaAs, etc.) and speculate on the future prospects for this new materials technology.
Improvement of Minority-Carrier Properties of GaAs on Si
Authors: Vernon S.M. , Ahrenkiel R.K. , Al-Jassim M.M. , Dixon T.M. , Jones K.M. , Tobin S.P. , Karam N.H.
Published: March 2011

GaAs-on-Si structures have been grown by atmospheric-pressure metalorganic chemical vapor deposition (MOCVD); in some samples, the GaAs nucleation layer was deposited by atomic layer epitaxy (ALE). Material quality has been characterized by Nomarski microscopy, time-resolved photoluminescence, trans- mission electron microscopy, and the performance of photovoltaic devices. The minority-carrier lifetime has been correlated with defect density and growth parameters. The use of a thermal-cycle-growth technique is seen to be a major factor in improving GaAs-on-Si material quality without resorting to the use of thick buffer layers.
Electronic Transport Properties of ZnSe Layers on GaAs
Authors: Marshall T. , Colak S. , Houten H. Van , Petruzzello J. , Greenberg B. , Cammack D.
Published: March 2011

The electronic transport properties of ZnSe layers grown by MBE on GaAs sub- strates are studied by small-signal ac admittance, dc current-voltage, and Hall effect measurements. This work is supplemented by a study of TEM and x-ray rocking curve data. We find that the transport characteristics are strongly affected by the proper- ties of the ZnSe/GaAs interface. From the dc and ac measurements, we determine the total barrier height at the interface of thick (1-6 µm) ZnSe layers on n+-GaAs, and find that it is in general voltage dependent. While some samples are found to have a very high peak mobility (> 10,000cm2 /Vsec), an anomalous reduction in the mobility in a large fraction of the samples is found, and attributed to the presence of non- uniform space charge regions.
Mocvd Growth of CdTe and HgTe on GaAs in a Vertical, High-Speed, Rotating-Disc Reactor
Authors: Tompa G.S. , Nelson C.R. , Reinert P.D. , Saracino M.A. , Terrill L.A. , Colter P.C.
Published: March 2011

The metalorganic chemical vapor deposition (MOCVD) growth of CdTe and HgTe on GaAs (111) and (100) substrates in a vertical, high-speed, rotating-disc reactor was investigated. A range of total reactor pressure, carrier gas flow rate, chemical concentrations, deposition temperature, and rotation rate have been investigated in an attempt to optimize growth conditions. Diisopropyltelluride (DIPTe) and Dimethylcadmium (DMCd) were used as growth precursors. Thickness uniformity varies less than +/- 1.5% over 50 mm diameter wafers. Films having FWHM X-ray rocking curves less than 90 arcsec were obtained on GaAs (111) substrates. The films have excellent surface morphology, exhibiting less than 5x104 cm-2 orange peel dents which are << 1 µm in size. An elemental mercury source was added to the growth system. Initial results for the growth of HgTe and HgCdTe will be discussed in this text.
InGaAs Compositional Control in a Halide-Based Vapor Levitation Epitaxy System
Authors: Yee Camellia M. L. , Davisson Pamela S.
Published: March 2011

The Vapor Levitation Epitaxy (VLE) system utilizes quartz frits directly in front of the growth surface of the substrate. This impacts on both epitaxial layer thickness uniformity and compositional uniformity. The highly uniform layers achievable with the process have been described.

In this paper we discuss the compositional uniformity of InGaAs epitaxial layers grown by the VLE process. The composition of the InGaAs is shown to vary with time during a growth run and across the wafer when using the same growth conditions as for an open tube halide system. This compositional variation occurs for InGaAs layers exceeding 1.5 μm in thickness. We show that with the proper gas phase composition, InGaAs epitaxial layers in excess of 5.0 μm thick can be grown with excellent compositional uniformity.
Kinetic Limits to Growth on GaAs by Omcvd
Authors: Aspnes D. E. , Bhat R. , Colas E. , Koza M. A. , Keramidas V. G. , Studna A. A.
Published: March 2011

Using a real-time surface probe with 0.01 monolayer (ML) sensitivity, we determine the rate-limiting steps for atmospheric-pressure, alternating-layer-epitaxy OMCVD growth on (001) and (110) GaAs with trimethylgallium and arsine sources. The reaction of TMG with AsH3- saturated (001) GaAs is limited by a competition between decomposition (at 39 kcal/mole) and desorption of TMG chemisorbed (at −26 kcal/mole) via an excluded-volume mechanism. The reaction of AsH3with TMG-saturated (001) GaAs shows an initial fast transient followed by a slower recovery. On (110) GaAs, TMG reacts essentially instantaneously with an AsH3-saturated surface while the reaction of AsH3 with a TMG-saturated surface is relatively slow. In the latter case temperature and pressure dependences indicate a fast AsH3 -surface reaction that is blocked by an adsorbed species that must be desorbed before the AsH3 -surface reaction can take place.
Silicon Carbide Structures Prepared by Rapid Thermal Chemical Vapor Deposition
Authors: Crowley J.L. , Liao J.C. , Kleins P.H. , Campisi G.J.
Published: March 2011

The deposition of beta Silicon Carbide unto single crystal silicon (100) wafers using rapid thermal chemical vapor deposition (RTCVD) has been carried out using silane and ethylene as the source gases. Deposition temperatures were varid from 1100°C to 1300°C. Auger analysis revealed the silicon carbide films to be stoichiometric at all temperatures. Infrared spectroscopy data taken between 1200 cm−1 and 60° Cm−1 show the appearance of the longitudinal optical phonon at 974 cm−1 and the transverse optical phonon at 794 cm−1 in samples deposited at 1200°C and above. Stress in the films deposited on the single crystal silicon substrates is seen to go from zero or slightly compressive at 11O0°C to strongly tensile at 1300°C.
GexSil-x Layers Grown by Rapid Thermal Processing Chemical Vapor Deposition
Authors: Jung K. H. , Kim Y. M. , Chun H. G. , Kwong D. L. , Rabenberg L.
Published: March 2011

Rapid thermal processing chemical vapor deposition was used to grow single and multilaye repitaxial GexSil-x/Si structures on (100)Si substrates using GeH4 and SiH2Cl2 at 900°C and 1000°C with SiH2Cl2:GeH4 ratios of 14:1 to 95:1 at 5 Torr. Misfit dislocation free layers with few threading dislocations were grown for Ge concentrations of up to 13%. Misfit dislocation networks aligned along <110> were formed at the interface of films with higher Ge concentrations. Dislocation loops were also found at the interface. GexSil-x layers grown at 1000°C were highly crystalline, but relaxed. In multi-layer structures, AES depth profiles showed Ge pile-up at the GexSi1-x/Si interface of layers with higher Ge concentrations.
Tungsten Film Formation on Silicon by Combining Ionic Decomposition of Metal Halides with Rapid Thermal Processing
Authors: Tidemand-Petersson Peer , SØRensen Gunnar
Published: March 2011

Thin films of tungsten metal and tungsten silicide were formed by combination of spin-on of tungsten chloride dissolved in a volatile organic solvent, decomposition of the chloride by ion bombardment and finally heating in a new versatile Rapid Thermal Processing (RTP) system. The films resulting from this treatment were characterized by Rutherford Backscattering Spectrometry (RBS) prior to and after the ionic decomposition and heat treatment. The procedure and the results of the analysis are described and discussed in terms of process conditions in this paper.
Thermal Stability in the /TiSi2/TiN/Al Metallization System
Authors: Hamdi A.H. , Alvi N.S. , Kermani A. , Al-Kaisi M.
Published: March 2011

Stability in the temperature range between 450°C and 525°C of reactively sputter deposited TiN and TiN formed simultaneously with TiSi2 using transient annealing has been investigated in the /TiSi2/TiN/Al metallization system.
Low-Temperature Self Aligned TiSi2'TiN Bilayer by Rapid Thermal Nitridation of Metastable Titanium Silicide in NH3 Ambient
Authors: Kermani Ahmad , Kuehne John
Published: March 2011

Rapid thermal nitridation (RTN) of metastable Ti silicide in pure ammonia ambient has been shown to result in the formation of a bilayer TiSi 2'TiN structure. This bilayer structure provides an effective self-aligned diffusion barrier against aluminum spiking. Further, the simultaneous formation of TiN on top of the TiSi2 preserves the low resistivity of the silicide layer upon subsequent high temperature process steps. Rutherford backscatttering spectroscopy, Auger electron spectroscopy and four point probe techniques were used to analyze the stoichiometry of the nitrided layer, and to study the kinetics of the nitridation reaction. The nitridation of the metastable silicide film is a substitutional eaction which begins at the surface of the silicide and progresses by substituting nitrogen atoms for silicon. The nitrogen atoms result from dissociation of ammonia The released silicon atoms then diffuse to the silicide'silicon interface and deposit in an epitaxial manner. The benefits of the proposed metallization scheme are substantiated by electrical characterization of the bilayer structure in comparison with a conventional process.
High-Quality Gate-Oxide Films for Low-Temperature Fabricated Poly-Si TFTs
Authors: Suyama Shiro , Okamoto Akio , Shirai Seiiti , Serikawa Tadashi
Published: March 2011

High-quality gate-oxide films for poly-Si TFTs (Thin Film Transistors) are successfully produced by oxygen-argon sputter deposition at a low temperature (200°C). Silicon-oxide films that are sputter-deposited in an oxygen-argon mixture has higher resistivity and breakdown field than films that are sputterdeposited only in argon and thermal oxides grown on poly-Si. Moreover, TFT field-effect mobilities are considerably improved by mixing oxygen into the sputtering gas, resulting in 350 cm2 /V.sec. Subthreshold slope and threshold voltage are also reduced to 5.5 V and 0.8 V/decade. A temperature-dependence measurement of the drain current shows that these improvements in TFT characteristics result from a lowering of the barrier height at the poly-Si grain boundaries, indicating a reduction in the trap density at these boundaries. Results confirm the usefulness of gate-oxide films that are sputter-deposited in an oxygen-argon mixture, for lowtemperature fabricated poly-Si TFTs.
Performance and Reliability of Ultrathin Oxynitride Gate Dielectrics Prepared using In-Situ Multiple Rapid Thermal Processing
Authors: Lo G. Q. , Shih D. K. , Ting W. , Kwong D. L.
Published: March 2011

The electrical characteristics of ultrathin oxynitride gate dielectrics prepared by in-situ multiple rapid thermal processing in reactive ambients (O2 and NH3) have been studied. Specifically, the conduction mechanism, charge trapping properties, time-dependent breakdown, and interface hardness in oxynitride films have been characterized as a function of both RTO and RTN processing parameters. In addition, N-channel MOSFET's have been fabricated using oxynitrides as gate dielectrics and their hot carier immunity has been examined and compared with devices with pure thermal oxides. Devices with superior electrical characteristics and reliability have been produced by optimizing RTO/RTN parameters.
Characterization of LPCVD of Silicon Nitride in a Rapid Thermal Processor
Authors: Johnson F. Scott , Miller Roderick M. , Öztüirk Mehmet C. , Wortman Jimmie J.
Published: March 2011

Low pressure chemical vapor deposition of silicon nitride has been studied using a cold-walled, lamp heated, rapid thermal processor. Films were deposited at low presure using both silane and dichlorosilane, diluted in hydrogen and argon carrier gasses. The dichlorosilane and ammonia reaction was found to be unsuitable for use in the cold-walled system. Rapid thermal chemical vapor depositions using silane and ammonia did not result in “bullseye” non-uniformities reported for low presure depositions in conventional hot-walled tube furnaces. Ammonia to silane ratios of 120:1 were found to result in stoichiometric silicon nitride films. Deposition rates are well suited for dielectricapplications. Electrical characteristics are comparable to those of films deposited using APCVD and LPCVD methods.
Long-Range Diffusion of Transition Metals in Silicon During Rapid Thermal Annealing
Authors: Sparks D.R. , Alvi N.S. , Sanders K.
Published: March 2011

A detailed comparison between transition metal diffusion results in silicon during rapid thermal annealing obtained in this and other studies with the diffusivity and solubility results obtained in the literature has been made. Using secondary ion mass spectroscopy, U-shaped diffusion profiles, possibly denoting amphoteric diffusion, have been noted fo Cu, Ni, and Pd in silicon during short anneals. Applications are reviewed.
Growth and Doping Kinetics of GexSil-x Structures by Limited Reaction Processing
Authors: Garone P.M. , Sturm J.C. , Schwartz P.V. , Schwarz S.A. , Wilkens B.
Published: March 2011

We have investigated the growth rate and boron doping of Sil-xGex epitaxial films grown by Limited Reaction Processing The growth experiments were carried out at a pressure of 6.0 torr with growth temperatures ranging from 625°C to 1000°C. The growth rate increases rapidly upon the additon of a small germane flow to the dichlorosilane in the reaction-rate-limited growth regime, and can not be explained simply by germanium incorporation. The presence of germane can increase the silicon growth rate by up to a factor of one hundred. Boron doping was also studied at high concentrations of boron in Si and Sil-xGex epitaxial films as a function of diborane flow and growth rate supports a simple kinetic model rather than an equilibrium model.
Spatial Inhomogeneities in Rapidly Thermal-Processed GaAs Wafer
Authors: Usami A. , Kitagawa A. , Wada T.
Published: March 2011

The spatial distributions of the midgap defect (EL2) concentration in semi-insulating liquid-encapsulated Czochralski GaAs wafers have been characterized by the contactless measurement of the optically injected carrier using reflectance microwave probe (RMP) method. The four-fold symmetrical distribution of EL2 in the (100) plane is observed in the 2 inch diameter GaAs wafer after rapid thermal processing(RTP). The deep level distribution in the RTP wafer corresponds to the crystallographic slip generation pattern obtained from x-ray topography. The correlation between the pattern of the redistributed EL2 concentration and the slip generation in the RTP wafer is suggested that the EL2 is produced by the large thermal stress during RTP. Furthermore, the distributions of EL2 center measured by the RMP method are compared with the dislocation patterns in undoped and In-doped GaAs wafers.
High Quality Si and Sil-xGex, Films and Heterojunction Bipolar Transistors Grown by Rapid Thermal Chemical Vapor Deposition (RTCVD)
Authors: Green M. L. , Brasen D. , Temkin H. , Kannan V. C. , Luftman H. S.
Published: March 2011

Rapid thermal chemical vapor deposition (RTCVD) is a processing technique that results from the combination of radiant heating lamps and a CVD chamber. It is the ultimate cold-wall CVD reactor and allows one to clean wafers in-situ and immediately thereafter deposit epitaxial layers. Very thin layers (<100 Å) can be deposited by either gas or lamp power switching. We report here the growth of high quality Si and Si-Ge layers, both intrinsic and in-situ doped, and the in-situ growth of a heterojunction bipolar transistor. These HJBT's show gains as high as 350 and are promising as microwave transistors. RTCVD processing is a production-worthy technology that will play an important role in the manufacture of future heterostructural devices.
Advanced Single-Wafer Sequential Multiprocessing Techniques for Semiconductor Device Fabrication
Authors: Moslehi Mehrdad M. , Davis Cecil
Published: March 2011

Single-Wafer Integrated in-situ Multiprocessing (SWIM) is recognized as the future trend for advanced microelectronics production in flexible fast turn-around computer-integrated semiconductor manufacturing environments. The SWIM equipment technology and processing methodology offer enhanced equipment utilization, improved process reproducibility and yield, and reduced chip manufacturing cost. They also provide significant capabilities for fabrication of new and improved device structures. This paper describes the SWIM techniques and presents a novel single-wafer advanced vacuum multiprocessing technology developed based on the use of multiple process energy/activation sources (lamp heating and remote microwave plasma) for multilayer epitaxial and polycrystalline semiconductor as well as dielectric film processing. Based on this technology, multilayer in-situ-doped homoepitaxial silicon and heteroepitaxial strained layer Si/GexSil-x/Si structures have been grown and characterized. The process control and the ultimate interfacial abruptness of the layer-to-layer transition widths in the device structures prepared by this technology will challenge the MBE techniques in multilayer epitaxial growth applications.