bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel Growth Techniques for the Fabrication of Photonic Integrated Circuits
Authors: Coudenys G. , Vermeire G. , Zhu Y. , Moerman I. , Buydens L. , Van Daele P. , Demeester P. 
Published: March 2011

INTRODUCTION:The fabrication of Photonic Integrated Circuits (PIC) requires the development of advanced growth and processing techniques. One of the major problems in the fabrication of PICs is the monolithic integration of passive and active waveguiding structures with a different bandgap. This is schematically shown in figure 1 where a laser, waveguide and detector are integrated on the same substrate. The following relationship between the different bandgaps is required : Eg (detector) < Eg (laser) < Eg (waveguide). One of the most advanced PICs is certainly a coherent receiver chip where a local DFB laser oscillator is integrated with a Y-junction, 3-dB splitter and balanced photodetector pair [1,2,3]. Current integration schemes are mostly based on the use of different epitaxial growth steps to obtain the different bandgap materials on the same substrate. In order to improve yield and performance it is required to reduce the number of growth steps by using special growth techniques. In this paper we will briefly describe some of the recent developments in advanced growth techniques. A more detailed description will be given of our recent work based on selective growth and shadow masked growth using Metal Organic Vapour Phase Epitaxy (MOVPE).
A Comparison Between Dry Etching with an Electron Cyclotron Resonance Source and Reactive Ion Etching for GaAs and InP
Authors: Pang S. W. 
Published: March 2011

ABSTRACTEtching with an electron cyclotron resonance (ECR) source provides several advantages over conventional reactive ion etching (RIE). In this work, the results of GaAs and InP etching using a multipolar ECR source are presented and compared to RIE. The effects of microwave and rf power, gas composition, pressure, and source to sample distance on the etch characteristics of GaAs and InP were evaluated. Three different etch gases were used including CCl2F2, BCl3, and Cl2. The influence of microwave power on etch characteristics is compared to conventional parallel plate system using rf power alone.
Electron Cyclotron Resonance Plasma Processing of GaAs-AlGaAs Hemt Structures
Authors: Pearton S. J. , Ren F. , Lothian J. R. , Fullowan T. R. , Kopf R. F. , Chakrabarti U. K. , HUI S. P. , Emerson A. B. , Pei S. S. 
Published: March 2011

ABSTRACTThe damage introduced into GaAs/AlGaAs HEMT structures during pattern transfer (O2 plasma etching of the PMGI layer in a trilevel resist mask) or gate mesa etching (CCl2F2/O2 or CH4/H2/Ar etching of GaAs selectively to AlGaAs) has been studied. For etching of the PMGI, the threshold O+ ion energy for damage introduction into the AlGaAs donor layer is ∼200 eV. This energy is a function of the PMGI over-etch time. The use of ECR-RF O2 discharges enhances the PMGI etch rate without creating additional damage to the device. Gate mesa etching produces measurable damage in the underlying AlGaAs at DC negative biases of 125–150V. Substantial hydrogen passivation of the Si dopants in the AlGaAs occurs with the CH4 /H2 /Ar mixture. Recovery of the initial carrier concentration in the damaged HEMT occurs at ∼400°C, provided the maximum ion energies were dept to ≤400 eV. Complete removal of residual AIF3 on the CCl2F2/O2 exposed AlGaAs was obtained after H2O and NH4 OH:H2O rinsing while chlorides were removed by H2O alone.
Selective Gate Recessing of GaAs/AIGaAs/lnGaAs Pseudomorphic HEMT Structures Using BCl3 Plasmas
Authors: Kazior T. E. , Patel B. I. 
Published: March 2011

ABSTRACTWet chemical gate recessing of GaAs based devices suffers from poor control and uniformity of the recess etch depth. Electrical variability can be particularly severe for heterojunction devices that contain thin highly doped layers. This problem can be addressed by the use of etch stop layers and the appropriate etch chemistry. In this paper, results on the selective plasma etching of GaAs from InGaAs and AIGaAs etch stop layers are presented. Using a BCl3 plasma, GaAs layers were removed from thin lnxGa(1-X)As (0.12<x<0.25) layers with selectivities >1000 to 1 due to the poor volatility of indium chlorides. With the addition of SFe, the etch process becomes selective to AlxGa (1-X)As due to the formation of a non-volatile AlFX layer. By the judicious choice of etch conditions (high pressure and low power resulting in low DC bias and optimal BCl3/SF6 ratio), isotropie etch profiles with minimal substrate damage and GaAs to Al0.25Ga0.75As selectivities >1000 to 1 have been achieved. Using these etch conditions, pseudomorphic HEMT wafers were selectively plasma gate recessed yielding saturated current uniformities across a 3 inch wafer of <±1.0mA/100μm of gate periphery. Device characteristics and uniformities that are dependent upon the material structure and epitaxial layer thickness and dopant uniformities rather than upon the gate recess process are realized.
Investigation of Gaas Deep Etching by Using Reactive Ion Etching Technique
Authors: Din Kuen-Sane , Chi Gou-Chung 
Published: March 2011

ABSTRACTRIE is an important technique in obtaining anisotropie etch profile. This is a critical requirement for very deep etching which needs long etch duration. Among many factors which affect RIE characteristics in deep etching, the following are most concerned: (1) the etch mask: needs suitable plasma resistance without significant plasma attack for extended etch time; (2) Long time stability in etch rate and surface conditions for the sample; (3) Etch profile: should be anisotropie with tolerable undercut In this work, CCl2F2 and SiCl4 were used with CCl2F2 as the main etchant. Ar was used in the initial stage for sputtering away surface residues prior to actual etching was performed. Three types of etch masks were prepared and their performance such as plasma was investigated. Multilayer metal etch mask has very low etch rate in plasma and its etch rate selectivity is around 300. The etch selectivities of GaAs to Si3N4 and to photoresist are 35 and 23, respectively. Etch mask can be chosen depending on the thickness of etch mask and the required GaAs etch depth. The etch rate of GaAs was found significantly increased when metal mask was applied. While PR mask is easier for inducing surface coating.
Novel ECR Reactor for Plasma Processing of III-V Semiconductor Compounds
Authors: Lane Baxton , Smatlak Donna 
Published: March 2011

ABSTRACTA novel electron cyclotron resonance (ECR) reactor for plasma processing of III-V compound semiconductors is presented. The reactor is appropriate for processes which are damage sensitive or for applications in which direct overhead access to the wafer is advantageous. The reactor uses an axisymmetric magnetic geometry provided by electromagnets and locates the source region below the wafer; there is no direct line of sight to the wafer from the plasma discharge region. The geometry allows more flexible neutral gas handling capabilities and frees the area above the wafer for diagnostics, neutral gas manifolds, energetic ion beam injection, laser irradiation of the wafer or vacuum pumping access. The combination of auxiliary processing with beams or laser light simultaneous with the plasma processing step opens possibilities for new processes, increased throughput and reduced wafer handling.
Rapid Growth Kinetics, Mechanical Properties and Thermal Stability of Siox Thin Films Grown by Rapid Thermal Low Pressure Chemical Vapor Deposition
Authors: Feingold A. , Katz A. , Pearton S. J. , Chakrabartl U. K. , Jones K. S. 
Published: March 2011

ABSTRACTHigh quality SiOx films were deposited onto InP substrates in the temperature range of 350 to 550°C and pressure range of 5 to 15 Torr. Depositions were made by means of rapid thermal low pressure chemical vapor deposition (RT-LPCVD) using oxygen (O2) and 2% diluted silane (SiH4) in argon (Ar) gas sources, with O2:SiH4 gas ratio of 5:1 to 50:1. High deposition rates of 15–50 nm/sec were obtained, providing uniform SiOx layers, with low stresses of −5×109 to −2×109 dyne-cm−2, and thermal stability on post deposition temperatures up to 1000°C. The SiOx films had refractive indexes between 1.44 and 1.50, densities of 2.25 to 2.37grcm−3 and exhibited wet etch rates of 0.2 to 0.8 nmsec.−1 through standard p-etch process. The influence of the various process parameters on the SiOx film properties was examined.
Ohmic Contacts to Heavily Carbon-Doped p+-GaAs Using Ti/Si/Pd
Authors: Lee H. S. , Han W. Y. , Lu Y. , Cole M. W. , Lareau R. T. , Casas L. , Thompson R. J. , Deanni A. , Jones K. A. , Yang L. W. 
Published: March 2011

ABSTRACTLow specific resistance ohmic contacts have been formed on heavily carbon doped GaAs using the Ti/Si/Pd system. Suicide formation was observed in the Pd/Si layers over the temperature range 400 – 700 C using RTA. Contact resistances as low as 0.061 Ω-mm and specific contact resistances as low as 3.2 × 10−6Ω;-cm2 were measured. Silicide/Ti/GaAs interfacial information was determined using TEM and Auger depth profiling.
Fabrication of Hemt-on-Si by Movpe for Lsi Applications
Authors: Ohori Tatsuya , Kikkawa T. , Suzuki M. , Takasaki K. , Romeno J. 
Published: March 2011

ABSTRACTWe grew selectively doped heterostructures on a Si substrate by metalorganic vapor phase epiaxy (MOVPE) for the first time and fabricated high electron mobility transistors (HEMTs). The conventional selective dry etching process to fabricate enhancement and depletion mode HEMTs on the same wafer, can be used without changing any process conditions. We evaluated the side-gate effect and obtained a critical voltage of 8V. This is large enough for LSI applications. We fabricated HEMTs on two kinds of GaAs-on-Si substrates. One had a small etch pit density (EPD) and poor surface morphology. The other had a large EPD, and better surface morphology. We compared the characteristics of devices on these two substrates, and the degradation of their characteristics was larger for the substrate with a small EPD and poor surface morphology. We conclude that improvement of surface morphology is more important than reduction of dis-location density. For the substrate with better surface morphology, maximum transconductance and K-value, for a gate length of 1 μm were 91% and 84% those of on-GaAs devices.
Direct Evidence for Interstitial Carbon in Heavily Carbon-Doped GaAs
Authors: HÖFler G. E. , Klatt J. , Baillargeon J. N. , Averback R. S. , Cheng K. Y. , Hsieh K C. 
Published: March 2011

ABSTRACTCarbon is a promising p-type dopant in GaAs/AlxGa1−xAs heterojunction bipolar transistors (HBT) because of its low atomic mobility and its potential for achieving very high carrier concentrations. It is generally believed that carbon incorporates substitutionally on the column V sublattice. However, an anomalous behavior at carrier concentrations > 5 × 1019 cm−3 is observed in the electrical properties of carbon doped layers. The strain sustained in these layers may be explained by the presence of interstitial carbon.We used Rutherford Backscattering Spectrometry in channeling geometry utilizing the nuclear reaction 12C (d,p)13C to determine the lattice locations of carbon in GaAs. The data presented unambiguously show, that up to 25% of the carbon atoms occupy interstitial sites. The presence of interstitial carbon is of importance for applications, since interstitial carbon may exhibit an enhanced diffusivity altering nominally abrupt dopant profiles.
Radiation Testing of AlInAs/lnGaAs and GaAs/AlGaAs HBTs
Authors: Witmer S. B. , Mittleman S. , Lehy D. , Ren F. , Fullowan T. R. , Kopf R. F. , Abernathy C. R. , Pearton S. J. , Humphrey D. A. , Montgomery R. K. , Smith P. R. , Kreskovsky J. P. , Grubin H. L. 
Published: March 2011

ABSTRACTThe radiation hardness of small geometry (∼2 × 4 μm2), state of the art AlInAs/lnGaAs and GaAs/AlGaAs HBTs to 60Co γ-ray has been investigated up to a dose of 100 MRad. The former devices showed a small change in Ic and gain for 20 MRad, with essentially no change in IB. At 40 MRad, the gain of the devices had decreased to unity. By contrast, for GaAs/AlGaAs HBTs, the current gain actually increased up to a dose of 75 MRad. At 100 MRad, none of our devices were still operational. This was ascribed to degradation of the base-collector contact metallization (TiPtAu) and in particular to the presence of Au. Carbon-and beryllium-doped base devices showed the same response to 60Co γ-ray doses. No long transient responses in either base or collector currents were observed during irradiation of the GaAs/AlGaAs devices with 120 nsec pulses of 10 MeV electrons at rates up to 2.7 × 1010 Rad · sec−1. Results of a 2-dimensional modelling study suggest that both GaAs and InP based HBTs are relatively immune to damage by transient radiation effects up to a dose rate of 1011 Rad · sec−1, with GaAs based devices being more resistant to radiation than InP due to their shorter recombination times.
High Electron Mobility Transistors with Optically Processed Refractory Silicide Metallizations: Thermal and Microwave Analysis
Authors: Tang P. F. , Fan M. S. , Illiadis A. A. 
Published: March 2011

ABSTRACTThe enhanced high temperature gate metallizations consisting of sputtered TiWSi or TiWN were investigated in order to attain high temperature stability at temperatures in excess of 250°C. The TiWN/Au system resulted in a sheet resistance of only 11.5 mΩ/□ while TiWSi/Au resulted in 75.0 mΩ/□. The HEMTs and FETs processed with additional stable ohmic contacts of epitaxial Ge/Pd structures exhibited a stable transconductance of 160 -180 mS/mm at temperatures of 300°C. Thermal analysis indicated the peak junction temperature increase with an input power of 200mW to be less than 18°C at substrate temperature of 60°C.
An Optically Gated InP Based Thyristor for High Power Pulsed Switching Applications
Authors: Zhao J. H. , Lis R. , Coblentz D. , Illan J. , McAfee S. , Burke T. , Weiner M. , Buchwald W. , Jones K. 
Published: March 2011

ABSTRACTAn MOCVD grown InP based optothyristor has been fabricated and tested for high power pulsed switching applications. To increase the power handling capability, the thyristor structure has a 250 μm thick Fe doped semi-insulating (SI) InP sandwiched between two pn junctions of a conventional thyristor. The turn-on of the thyristor is controlled by optical illumination on the SI-InP which creates a high concentration of electron and hole pairs. More than 1,100 V device hold-off voltage has been observed and over 66 A switched current has been realized with a di/dt rating of 1.38×1010 A/s. The switched current as a function of switch voltage and of optical illumination power has also been studied. Comparison with the switching characteristics of a bulk SI-InP photoconductive switch clearly indicates the advantage of this optothyristor in terms of power handling capability.
The Impact of the Extrinsic Device on HFET Performance
Authors: Greenberg David R. , Del Alamo Jesús A. 
Published: March 2011

ABSTRACTThe extrinsic device is known to degrade the performance of heterostructure field-effect transistors (HFET's) through the introduction of a parasitic source resistance (Rs). To date, however, there has been no recognition of the fact that carrier velocity saturation (vsat) can occur in both the extrinsic source and drain, setting the ultimate limit on maximum drain current (I,D,max) and on the useful VGS swing in HFET's. In this study, we demonstrate the mechanisms through which vsat in the extrinsic device limits device performance, using AlGaAs/n+-InGaAs Metal-Insulator-Doped-channel FET's (MIDFET's) as a vehicle. These devices show that gm falls at a lower VGSthan does fT, by as much as 1 V. This reveals that there are two mechanisms at work. The approach of vsat in the extrinsic source first causes the small-signal source resistance (Ts)to rise rapidly, leading gm to decline but leaving fT unaffected. As the carrier velocity in the extrinsic device approaches Vsat more closely, there is an actual decline of the carrier velocity in the intrinsic device. This process degrades velocity-related figures of merit such as and fT.
Theoretical Studies of Defects, Impurities, and Complexes in Semiconductors
Authors: Estreicher Stefan K. 
Published: March 2011

ABSTRACTTheoretical studies of microscopic properties of localized defects, impurities, and complexes in semiconductors have greatly progressed in the past decade. Theory has advanced beyond “point” defects to include lattice relaxations and distortions, interactions between defects, complex formation, and even some extended structures. Vibrational frequencies, hyperfine parameters, and other measurable quantities are being calculated from first principles. Both the one-effective-particle density-functional approach and the all-electron Hartree-Fock methods are able to predict a variety of microscopic properties of defects at or near the ab initio level. However, despite the progress achieved, theoretical descriptions only approximate the real world. In this paper, an overview is given of the way these calculations are done and of the main approximations involved. Although some of them will be eliminated by progress in computer technology, other problems such as electron correlation or excited states are likely to require new thinking.
Dose effects in Si FIB-mixing of short period AlGaAs/GaAs superlattices
Authors: Stecki A. J. , Chen P. , Choo A. , Jackson H. , Boyd J. T. , Pronko P. P. , Ezis A. , Kolbas R. M. 
Published: March 2011

ABSTRACTResults are presented on FIB mixing of an Al0.3Ga0.7As/GaAs superlattice with equal 3.5 nm barrier and well widths. Si++ was accelerated to 100 kV and implanted parallel to sample normal at doses ranging from 1013 to 1015/cm2. The level of inter-layer disordering was measured primarily by Auger depth profiling. The mixing effect of RTA-only increased roughly linearly with annealing time at both 950 and 1000°C, with the latter exhibiting a sharper slope. At either temperature, 90 s was sufficient to produce complete mixing within the accuracy of the measurement. An anneal of 10 s at 950°C, which was utilized in subsequent post-implantation annealing, resulted in ∼ 25% thermally-induced mixing, with a corresponding PL “blue shift” of 6 meV. The level of mixing by an ion dose of 1 × 1014/cm2 yielded a mixing parameter of 0.87, where 1.0 represents complete mixing. This is the lowest ion beam dose necessary for nearly complete mixing reported to date for either FIB or BB implantation. Doubling the dose to 2 × 1014/cm2 results in an increase in mixing by only 0.05 to 0.92. Larger doses produced a diminishing increase in mixing parameter.
Correlation of Dislocation Loop Formation and Time Dependent Diffusion of Implanted P-type Dopants in Gallium Arsenide
Authors: Robinson H. G. , Deal M. D. , Stevenson D. A. , Jones K. S. 
Published: March 2011

ABSTRACTRecent experimental results indicate that diffusion of implanted p-type dopants in GaAs is time dependent under certain conditions. For Mg implanted at a dose of 1 × 1014 cm−2, the diffusion is constant for approximately an hour, then decreases by an order of magnitude or more. Be implanted at 1 × 1013 and 1 ×1014 cm−2 exhibits similar behavior, but with a shorter time before the diffusivity decreases. The diffusivity in 1 × 1013 Mg cm−2 implants, in contrast, remains constant for up to 16 hours. TEM micrographs of Be and Mg implants reveal dislocation loops in the higher dose samples, but not in the lower dose ones. During annealing, the loops grow and decrease in density, eventually disappearing completely from the crystal. This annealing of the loops appears to correlate to the time dependence of the diffusion. This behavior can be explained in terms of the substitutional-interstitial diffusion (SID) mechanism and point defect equilibria.
Ion Implantation Doping of InGaP, InGaAs, and InAlAs
Authors: Pearton S. J. , Kuo J. M. , Hobson W. S. , Hailemarian E. , Ren F. , Katz A. , Perley A. P. 
Published: March 2011

ABSTRACTThe activation of Si+ and Be+ ions implanted into InGaP, InGaAs or InAlAs grown by GSMBE and OMVPE was investigated as a function of ion dose and annealing temperature. Activation efficiencies close to 100% were obtained in InGaP and InGaAs for Be doses up to ∼1014 cm−2 and annealing temperatures of 700–850°C. Activation of Be was less efficient in InAlAs. By contrast, implanted Si displayed a saturation in active sheet electron densities at 1–3 × 1013 cm−2 and required higher annealing temperatures for optimum activation efficiency. High sheet resistance (≤108 μ/□) regions were created by O+ implantation into n+ InGaP or InAlAs, with hopping conduction dominating carrier transport in the bombarded material. For post-implant annealing temperatures above 750°C, the conductivity was restored to its initial value. No evidence was found for the creation of electrically active oxygen-related deep levels in either material.
High-Energy Elevated Temperature Si and Room Temperature B Implants in InP
Authors: Nadella R. K. , Vellanki J. , Rao M. V. 
Published: March 2011

ABSTRACTHigh-energy (3 MeV) Si implantations were performed in InP:Fe at an elevated temperature of 200 °C for fluences 8×1014, 2×1015, and 5×1015 cm“2. For the 8×1014 cm−2 fluence, an activation of 82 %, carrier mobility of 1200 cm2/V-s, a peak carrier concentration of 9×1018 cm−3, and lattice quality comparable to that of virgin crystal were obtained. No amorphization takes place for any of the fluences used. Boron compensation implantations were performed in InP:Sn (n sime 2×1018 cm3) at room temperature in the energy range 1 to 5 MeV and fluence range 1011 to 1015 cm−2. After heat treatment, maximum resistivity of the order of 106 Ω-cm was obtained in B implanted InP.
Amphoteric Behaviour of Ge in InP: A RBS/Channeling and Differential Hall/Resistivity Study
Authors: Kringhøj P. 
Published: March 2011

ABSTRACTThe lattice location of ion implanted Ga, Ge, and Se in InP has been determined with a combined RBS/channeling-PIXE technique and correlated to the carrier concentration and mobility profiles obtained with differential Hall/resistivity measurements.
The Electrical and Optical Properties of GaAs with as Precipitates (GaAs:As)
Authors: Warren A. C. , Woodall J. M. , Burroughes J. H. , Kirchner P. D. , Heinrich H. K. , Arjavalingam G. , Katzenellenbogen N. , Grischkowsky D. , Melloch M. R. , Otsuka N. , Mahalingam K. , Pollak F. H. , Yin X. 
Published: March 2011

ABSTRACTSince its initial report by the IBM/Purdue University group in 1990, GaAs with As precipitates (GaAs:As) has been shown by this group to exhibit unusual and useful electrical and optical properties. In this paper we review our progress in understanding the fundamental properties of this material. We have shown that both the electrical and optical properties of GaAs:As arc explained by assuming that the GaAs is of good crystalline quality and that the As precipitates act as buried Schottky barriers. This model accounts for its semi-insulating stability against both n- and p-type doping, its high-speed photoconductive behavior, and its ability to detect 1.3 micron light when it forms the “I” layer of a PIN photodiode via the internal photoemission process. Using modulation spectroscopy we clarify the fundamental differences between GaAs:As and unannealed GaAs grown at 200 C. We also show that GaAs:As used as a 1.3 micron detector in the metal-semiconductor-metal device structure format, has a photoconductive bandwidth in excess of 50 GHz.