bluuebunny/crossref_metadata_2025_split huggingface dataset:
AES and EELFS Studies of Initial Stages of Growth of GaAs/InAs/GaAs Heterostructures.
Authors: Schowengerdt F. D. , Grunthaner F. J. , Liu John K. 
Published: March 2011

ABSTRACTWe report on a systematic study of the composition and structure of GaAs/InAs/GaAs quantum wells using Auger Electron Spectroscopy (AES), Extended Energy Loss Fine Structure (EELFS), and Reflection High Energy Electron Diffraction (RHEED) techniques. Double heterostructures with InAs thickness ranging from 2 to 10 monolayers, capped by 2 to 10 monolayers of GaAs, were grown by MBE using a variety of techniques, including those employing sequential, interrupted, and delayed shutter timing sequences. AES peak ratios are compared with model calculations to monitor compositional development of the multilayers. The AES results are correlated with RHEED measurements to determine MBE growth parameters for optimal control of the stoichiometry and surface morphology. EELFS was used to monitor strain in the buried InAs layers. The AES results show departure from smooth laminar growth of layers of stoichiometric InAs on GaAs at temperatures below 420 C and above 470 C. AES results on the quantum well structures suggest floating InAs layers on top of the GaAs and/or facet formation in the GaAs layers. The EELFS results, when compared to bulk InAs, indicate the presence of strain in the buried InAs quantum well.
Characterization of III-V Semiconductor Structures Using Electron Beam Electroreflectance (EBER) spectroscopy.
Authors: Herman M. H. , Ward I. D. , Buttrill S. E. , Francke G. L. 
Published: March 2011

ABSTRACTEBER is a form of modulated reflectance spectroscopy in which a low energy electron beam alters the sample surface potential. For III-V semiconductors, the spectra are characteristic of electroreflectance, including excitonic, interband, and impurity transitions. The study of these transitions provides accurate estimations of band gaps in bulk and thick film samples. Measurements of the band gap energy in compounds such as AlxGa1-xAs provide highly precise evaluations of their composition.Additionally, EBER spectra of quantum well structures and heterojunctions provide useful information about the composition and quality of materials and interfaces. For quantum wells, detected features suggest the presence of allowed, disallowed, and resonant states. In EBER spectra of HEMT structures, peaks are apparent resulting from transitions between the valence band and the states in which the electrons are confined. We present examples of EBER determination of AlGaAs composition, single GaAs/AlGaAs quantum well evaluation, and HEMT characterization.
The Effect of Substrate Orientation on the Properties of (Ga, Al)As Grown by Gas Source Molecular Beam Epitaxy
Authors: Sandhu A. , FUJII T. , Ando H. , Ishikawa H. , Miyauchi E. 
Published: March 2011

ABSTRACTWe have carried out the first systemmatic investigation on the effect of substrate temperature and arsenic partial pressure on the morphology, growth rate, and compensation ratio of Si-doped GaAs, and the Al content of AlxGa1−xAs grown on just-cut (100), (110), (111)A&B, (311)A&B orientated GaAs substrates by gas source MBE (GSMBE). Triethylgallium ( TEG, Ga(C2H5)3 ) and triethylaluminium ( TEA, Al(C2H5)3 ) were used as group III sources, and solid arsenic ( As4 ) and silicon as a group V and IV sources, respectively. The best GaAs mophology was obtained at relatively high temperatures and arsenic pressures. The A orientations were identified as ‘fast surfaces,’ with the GaAs growth rate being comparable to the (100) orientation. The B orientations were identified as ‘slow surfaces,’ with the GaAs growth rate being much less (approximately 50% for the (111)B orientation ) than on the (100) orientation. The least compensated Si-doped GaAs was grown on the (311)A orientated substrate. The Al content, x, (nominally x=0.27 for (100)) of AlxGas1−xAs grown on (110), (111)A&B, was less than 0.05 and not affected by the growth conditions. The Al content of epilayers grown on (311)A&B ranged between x=0.1 to 0.27, strongly depending on the growth temperature.These results show that using GSMBE we can selectively modifying a large range of (Ga,Al)As crystal properties. Potential applications include the selective growth and realisation of ultra-fine and planar structures and devices.
Photoluminescence of InP/GaAs/Si Heterostructures
Authors: Mazzi V.P. , Haegel N.M. , Vernon S.M. , Haven V.E. 
Published: March 2011

ABSTRACTLow temperature photoluminescence results from MOCVD epitaxial InP grown on GaAs/Si substrates are presented as a function of thickness of the GaAs buffer layer. As a consequence of thermal expansion mismatch of the heterostructure, the InP layer contains residual stress which causes the band gap to shift and splits the valence band degeneracy of the mj = ± 3/2 and the mj = ± 1/2 bands. Both the shifting and splitting phenomena are clearly seen in tite PL results and are shown to depend on the GaAs buffer layer thickness.
Migration-Enhanced Molecular Beam Epitaxial Growth and Characterization of GaAs on Si Substrates
Authors: Kim J.H. , Sakai S. , Liu J.K. , Raohakrishnan G. , Chang S.S. , Katz J. , El-Masry N.A. 
Published: March 2011

ABSTRACTWe first report on migration-enhanced molecular beam epitaxial (MEMBE) growth and characterization of the GaAs layers on Si substrates (GaAs/Si). Excellent surface morphology GaAs layers were successfully grown on (100) Sisubstrates misoriented 4 toward [110] direction. The MEMBE growth method isdescribed and material properties are compared with those of normal two-step MBE-grown or in-situ annealed layers. Micrographs of cross-sectional view transmission electron microscopy (TEM) and scanning surface electron microscopy (SEM) of MEMBE-grown GaAs/Si showed dislocation densities of 107 cm-2 over ten times lower than those of two-step MBE-grown or in-situ annealedlayers. AlGaAs/GaAs double heterostructure lasers and light-emitting diodeshave been successfully grown on MEMBE GaAs/Si by both metal organic chemical vapor deposition and liquid phase epitaxy. MOCVD-grown lasers showed peak output power as high as 184 mW/facet, pulsed threshold currents as low as150 mA at 300 K, and differential quantum efficiencies of up to 30 %. The LPE-grown light-emitting diodes showed output powers of 1.5 mW and external quantum efficiencies of 3.3 mW/A per facet.
Thermal Stability of EL2 in GaAs
Authors: Boddaert X. , Letartre X. , Stievenard D. , Bourgoin J. C. 
Published: March 2011

ABSTRACTDifferent samples originating from the same LEC ingot have been used in order to determine the variation of the EL2 concentration versus depth after different types of thermal annealing ( 450 and 850°C : the temperatures generally used in technological processes ). The annealing of EL2 near the surface at 850°C has been interpreted as the result of the deviation from the stoichiometry near the surface, due to [As] variation induced by vacancy diffusion. At 450°C, the annealing of EL2 can only be explained by the dissociation of a complex, followed by the migration of one of the constituants, confirming that the EL2 defect is the complex AsGa- Asi.
X-Ray Studies of GaAs/Si and ZnS/Si
Authors: Kim H. M. , Choi Y-W , Vernon S. , Moise P. S. , Wie C. R. 
Published: March 2011

ABSTRACTThe MOCVD-grown layers of GaAs/Si(001), InP/GaAs/Si(001), and ZnS/Si(111) were studied using X-ray rocking curve (XRC), double crystal topography (DCT), and Nomarski phase contrast microscopy. The layer qualities of GaAs/Si, InP/GaAs, and InP/GaAs/Si from the XRC full width at half maximum (FWHM) agreed well with these determined from the Nomarski phase contrast microscopy. The in-plane lattice mismatch (parallel X-ray strain) was 3.71% for GaAs/Si. In the double heteroepitaxial layer (InP/GaAs/Si), the parallel X-ray strain of GaAs was 4.03% with respect to Si. The parallel X-ray strain was larger than the perpendicular X-ray strain in GaAs/Si, perhaps due to the mismatch in thermal expansion coefficients between GaAs and Si. Dislocation densities estimated from the rocking curve linewidth were 5.30 × 107 cm−2 for GaAs/Si, 3.27 × 108 cm−2 for InP/GaAs. We also present the double crystal X-ray topographs of the III-V/Si and II-VI/Si samples.
Relationship Between Electrical Activation and Residual Defects in MeV Si Implanted GaAs.
Authors: Braunstein G. , Zheng L.-R. , Chen Samuel , Lee S.-Tong , Peterson D.L. , Ko K.-Y. , Rajeswaran G. 
Published: March 2011

ABSTRACTWe have investigated the relationship between electrical activation and residual defects in GaAs implanted with 1 MeV Si ions to a fluence of 3×1015 cm−2 and subsequently annealed, using rapid thermal annealing (RTA) for 10 seconds, at temperatures up to 1050°C. Hall measurements show n-type activation that increases in magnitude with increasing annealing temperature to reach a sheet carrier concentration of 2.6×1014 cm−2 after RTA at 1050°C. Two main types of extended defects, perfect and partial dislocation loops, had previously been identified in the as-implanted samples. In addition, a large number of discrete point defect complexes are certainly created but escape detection. We show here a correlation between the annealing of the defects and the recovery of the electrical transport properties. Most of the point defects anneal out between room temperature and 700°C, and it is in this temperature regime that the transport properties show their most significant improvement. For annealing temperatures between 700°C and 1050°C, the mobility of the carriers decreases slightly while the carrier concentration gradually approaches saturation. Concurrently, the loops grow in size while decreasing in number and eventually anneal out. However, after annealing at 1050°C, while most of the extended defects have disappeared, only about 9% of the implanted atoms had been activated, suggesting that residual point defect centers control the activation of Si dopants in MeV implanted GaAs.
Rapid Thermal Annealing and Ion Implantation of Heteroepitaxial ZnSe/GaAs
Authors: Skromme B.J. , Stoffel N.G. , Gozdz A.S. , Tamargo M.C. , Shibli S.M. 
Published: March 2011

ABSTRACTWe describe the effects of rapid thermal annealing on the photoluminescence (PL) and electrical properties of heteroepitaxial ZnSe grown by molecular beam epitaxy on GaAs, using either no cap or plasma-deposited SiO2, Si3N4, or diamond-like C caps, and annealing temperatures from 500 to 800°C. Capless anneals (in contact with GaAs) produce badly degraded PL properties, while capped anneals can prevent this degradation. We show that Si3N4 is significantly more effective in preventing Zn out-diffusion through t e cap than previously employed SiO2 films, as evidenced by less pronounced PL features related to the creation of Zn vacancies during the anneal. Implant damage tends to enhance the Zn vacancy formation. Rapid thermal annealing with Si3N4 caps is shown to optically activate shallow N acceptor implants.
GaAs/AlGaAs Quantum Well Mixing Using Low Energy Ion Implantation and Rapid Thermal Annealing
Authors: Elman B. , Koteles Emil S. , Melman P. , Armiento C. A. 
Published: March 2011

ABSTRACTLow energy ion implantation followed by rapid thermal annealing (RTA) was utilized to modify exciton transition energies of MBE- rown GaAs/AlGaAs quantum wells (QW). The samples were irradiated with an 75As ion beam with an energy low enough that the depth of the disordered region was spatially separated from the QWs. After RTA, exciton energies (determined using optical spectroscopy) showed large increases which were dependent on QW widths and the implantation fluence with no significant increases in peak linewidths. These energy shifts were interpreted as resulting from the modification of the shapes of the as-grown QWs from square (abrupt interfaces) to rounded due to enhanced Ga and Al interdiffusion in irradiated areas. These results are similar to our data on the RTA of the same structures capped with SiO2 and are consistent with the model of enhanced intermixing of Al and Ga atoms due to diffusion of vacancies generated near the surface.
Mechanisms for Ion and Te-Induced Intermixing of GaAs-AlGaAs Interfaces.
Authors: Kahen K. B. , Rajeswaran G. 
Published: March 2011

ABSTRACTRecently, GaAs-AlGaAs interfaces have been interdiffused following furnace and rapid thermal annealing (RTA) of samples containing impurities. Two models are proposed to explain the events occurring during the annealing processes. Te was chosen as the impurity for furnace annealing, whereas for the case of RTA, the impurities were introduced via ion implantation. The Te-induced interdiffusion process is modeled using an ensemble Monte Carlo simulation. The results of the simulation are in good agreement with the Te intermixing data. In the case of ion implantation followed by RTA, the intermixing model is based on the solution of coupled diffusion equations involving the excess vacancies and the Al distribution following ion implantation. Both initial distributions are obtained from the solution of a three-dimensional Monte Carlo simulation of ion implantation into a heterostructure sample. The excess interstitials calculated in the simulation are coupled to the vacancy diffusion via a phenomenological decay constant. Having established the value of the decay constant from one set of experimental results, the model is able to predict accurately other independent experimental results.
Gallium Arsenide Surface Inversion using a Novel Silicon–Silicon Dioxide Insulator Structure
Authors: Fountain G.G. , Rudder R.A. , Hattangady S.V. , Markunas R.J. , Vitkavage D.J. 
Published: March 2011

ABSTRACTA novel GaAs metal insulator semiconductor (MIS) structure in which the surface of the GaAs is unpinned and inverted is reported. The structure utilizes a thinsingle crystalline Si interlayer between the GaAs surface and a SiO2 insulator. The Si and SiO2 are deposited using low temperature remote plasma chemical vapor deposition techniques. Characteristics of the Si layer have been examined using reflecting high energy electron diffraction, Xray photoelectron spectroscopy, and He ion scattering spectroscopy. The complete MIS structure has been characterized using capacitance-voltage data taken at frequencies ranging from near D.C. (quasistatic) to 100 MHz. The structure exhibits deep depletion and inversion behavior. Calculation of the surface potential variation using quasistatic data indicates that the surface potential is varied by 0.83 V with an applied electric field from −1.6 to 3.2 MV- cm−1.
A Tem Study of Optically Annealed Ohmic Contacts to GaAs Using a Zirconium Diboride Diffusion Barrier
Authors: Grimshaw Mike , Staton-Bevan Anne 
Published: March 2011

ABSTRACTThe morphology of a Ni(5nm), Au(45nm), Ge(20nm) ohmic contact with a ZrB2 (50nm) diffusion barrier, annealed to temperatures between 355°C and 485°C, was studied by TEM. The barrier was found to remain intact and unreacted after annealing. The contact annealed to 355°C reacted in the solid state to form αAu-Ga, Ge and orthorhombic NiGe phases. The morphology of contacts annealed above the melting point (∼ 380°C) consisted of two regions; type A contained αAu-Ca and NiGeAs, and type B contained αAu-Ga α′Au-Ga, NiGe and epitaxial Ge. αAu-Ga segregated to the contact pad edges at and above 403°C. The transition from rectifying to ohmic properties corresponded to annealing above the melting point of the contact. It was found that variations in contact resistance with temperature could be explained either by changes in the bulk or in the edge morphology.
Thermodynamically Stable Conducting Films of Intermetallic PtGa2 on Gallium Arsenide
Authors: Sadwick Larry P. , Wang Kang L. , Shuh David K. , Kim Young K. , Williams R. Stanley 
Published: March 2011

ABSTRACTThe first epitaxial platinum gallium two (PtGa2) films have been grown on gallium arsenide (GaAs) (100) by co-evaporation of the elements under ultra-high vacuum conditions. An electron beam evaporator and a Knudsen cell were used to produce the platinum and gallium beams, respectively. The resulting films and bulk PtGa2 have been characterized by x-ray diffraction, Auger electron spectroscopy, and x-ray photoelectron spectroscopy. The data confirm the PtGa2 stoichiometry and crystal structure of the films, and demonstrate their chemical stability on GaAs (100). This study supports the contention that PtGa2 can be a suitable, temperature stable contact material on GaAs substrates.
Amorphous WSi0.45 Metallization for Self-Aligned GaAs MESFETs
Authors: Lahav Alex 
Published: March 2011

ABSTRACTCrystallization temperature (Tc) of amorphous WSix films on GaAs was studied as a function of the Si/W ratio. The highest Tc of 875°C for a 20 min anneal was obtained for co-sputtered WSMi films with the Si/W ratio of 0.45 (31 at.% Si). The WSi0.45 films remained amorphous following implant activation anneal and served as a barrier to Ga and As outdiffusion. Pitting of GaAs under the contact was also prevented. The WSi0.45 composition corresponds to the eutectic point between the W and W5Si3 phases, which was explained by the strong glass-forming tendency of eutectic alloys. Amorpous WSi0.45 films formed stable Schottky contacts to n-GaAs and produced minimum reduction of carrier concentration in the substrate. Therefore, the Si/W ratio of 0.45 is suggested as optimal for the WSix refractory gate metallization in self-aligned GaAs MESFErs.
High Barrier Height MIS Diodes on n-InP Using Pd, Ni and Au on a Chemical Oxide
Authors: Lee Y. S. , Anderson W. A. 
Published: March 2011

ABSTRACTMIS diodes were fabricated using Pd, Ni and Au- contacts on n-InP covered by a 40 Å chemically-grown oxide. The oxide had a refractive index of 1.4–1.6 with a composition of mainly In2O3 + some InPO3 near the surface and mixed oxide + InP near the interface. Pd-devices gave the highest barrigr height of 0.80 eV and lowest reverse saturation current density of 3×10−8A/cm2. I-V-T and C-V-T data gave temperature dependence of barrier height and revealed an interface state recombination current mechanism. Richardson plots gave good straight lines when empirically corrected using øB/n instead of just øB.
The Challenge of GaAs Heterojunction Bipolar Transistor Integrated Circuit Technology.
Authors: Yuan Han-Tzong 
Published: March 2011

ABSTRACTThe status and progress of AlGaAs/GaAs heterojunction bipolar transistor integrated circuits are reviewed. The challenge of fabricating large-scale integrated circuits using heterojunction bipolar transistors is discussed. Specifically, the issues related to low defect epitaxial materials, localized impurity doping techniques, simple and reliable ohmic contacts, and multilevel interconnects are examined.
GaAs Heterojunction Bipolar Transistor Device and IC Technology
Authors: Kim Michael E. , Oki Aaron K. , Camou James B. , Gorman Gary M. , Umemoto Donald K. , Hafizi Madjid E. , Pawlowicz Leszek M. , Stolt Kjell S. , Mulvey Virginia M. 
Published: March 2011

ABSTRACTGaAs/AlGaAs N-p-n heterojunction bipolar transistor (GaAs HBT) device and integrated circuit technology which offers key advantages over advanced silicon bipolar and III-V compound field-effect transistors is maturing towards system insertion. The TRW device and IC fabrication process, basic HBT dc and RF performance, examples of device and IC applications, and technology qualification work are presented and serves as a basis for discussing overall technology issues and impact. A relaxed 3-μm emitter-up, self-aligned base ohmic metal (SABM) HBT process and simplified molecularbeam epitaxial profiles are used for near-term producibility. The HBTs have simultaneous fT, fmax≈20–40 GHz and dc current gain ß≈50–100 at collector current density JC=3 kA/cm2 and Early voltage VA≈200–300 with capability for MSI-LSI integration levels. Versatile dc-20 GHz analog, 3–6 Gb/s digital, and 2–3 Gs/s A/D conversion functions are demonstrated with a common 3-μm SABM HBT process which facilitates single-chip multifunctional capability. Key improvements are realized over Si bipolar and GaAs-related FET (e.g. MESFET and HEMT) approaches in operational frequency, gain-bandwidth product, harmonic distortion, 1/f noise, power consumption, and size reduction.
Redistribution Effects for OMVPE InP/GaAs
Authors: Tae-IL OH , Leigh Wallace B. 
Published: March 2011

ABSTRACTWe have analyzed the redistribution parameters for InP grown by organometallic vapor phase epitaxy (OMVPE) on GaAs substrates. The layers, grown using (trimethyl Indium) TMIn at atmospheric pressure, have been characterized for epitaxial quality using photoluminescence, energy dispersed x-ray analysis, and optical microscopy. In order to better understand the effects of inter-diffusion and inter-mixing for the GaAs into the InP epitaxial layer, the layer-substrate interface was first probed by growing consecutive samples of InP for increasingly longer growth times, and thus characterizing the layers as one moves away from the interface. For more detailed analysis, cross-sections of the InP/GaAs interface were prepared for scanning transmission electron microscopy (STEM). Energy dispersed x-ray analysis has shown that all elements In, Ga, As, and P, are present on the epitaxial side of the interface, while only Ga and As are present on the substrate side. A combination of electron diffraction and luminescence measurements show the epitaxy is at least 80% InP at the interface and essentially 100% InP at a distance of 6000Å into the epilayer. Electron diffraction and bright field investigation at the interface show the existence of a second phase, existing in a mostly InP matrix. The effects of redistribution in heteroepitaxial InP/GaAs will be discussed.
X-Ray, Photoluminescence and Etching Studies of Indium-Doped LPE GaAs Layers
Authors: Chen J.F. , Wie C. R. , Junga F. A. 
Published: March 2011

ABSTRACTThe effects of In doping on the structural properties of liquid phase epitaxially (LPE) grown GaAs layers are studied. The distribution coefficient of In in the GaAs at 800 ° C was determined to be 0.033 which was consistent with the value calculated from the pseudobinary phase diagram of the ternary system at a dilute In concentration. The full widths at halfmaximum (FWHM) of x-ray double crystal rocking curves show that a GaAs epi-layer of good crystalline quality can be obtained by doping In to a concentration up to 4.3 × 1019 cm−3, beyond which a sharp increase in the FWHM is observed. Etch pit density (EPD) measurement shows that the dislocation density is reduced by doping the epi-layer with In. At the optimal In concentration of 2.4 × 1019 cm−3, the EPD is reduced by a factor of 20 when measured at the surface of a 9 um thick epilayer.Photoluminesce measurements made at 15 K show two sharp emission spectra near the bandedge. The relative intensities of the two emissions, I(l.49eV)/I(l.5eV) are reduced with increasing In content. This suggests that incorporation of Carbon acceptors is suppressed by In doping in the GaAs epilayers. The FWHM as small as 5 meV of the bandedge transition was obtained for the epi-layer doped with In concentration of 2.4 × 1019 cm−3.