bluuebunny/crossref_metadata_2025_split huggingface dataset:
Energy and Depth Distributions of Interface States and bulk Traps and their Electronic Effects in GalnAs/GaAs Heterojuntions
Authors: Huang Z. C. , Wie C. R. , Johnstone D. , Stutz C. E. , Evans K. R. 
Published: March 2011

ABSTRACTWe have studied the lattice-mismatch-induced defects both at the interface and in the bulk (GaAs buffer layer ) of Ga0.92In0.08As/GaAs heterojunctions by means of C-V characteristics and constant capacitance deep level transient spectroscopy (CC-DLTS). The Ga0.92In0.08As (n+)/GaAs (P) samples, with the thickness of GalnAs layer at 0.1μm, 0.25μm, 0.5μm, and 1.0μm, were grown by MBE. The depth profiles of bulk hole traps in the GaAs buffer layer were measured by the DLTS technique as a function of the in-plane lattice mismatch. The concentration of lattice-mismatch-induced traps decreased exponentially with distance away from the interface. The depth distributions of the mismatch-induced bulk traps appeared to be affected by the pre-existing bulk traps and the dopant impurities in the GaAs buffer layer. Energy distribution of the interface states was obtained by the CC-DLTS and C-V measurements independently. All heterojunctions showed a minimum in the interface state density at about EV+0.83eV. The U-shaped energy distribution with donor- and acceptor-like states is interpreted by the disorder-induced-gap-states model.
Bonding of Hydrogen Implanted at 80K INTO III-V Semiconductors
Authors: Stein H. J. 
Published: March 2011

ABSTRACTHydrogen implantation at 80K is shown to introduce As-H centers in GaAs and InAs, and P-H centers in InP. These As (P)-H centers anneal between 150 and 300K. By analogy to suggested defect assignments in electron-irradiated GaAs, it is suggested that the sites for the As (P)-H centers are metastable defects such as close vacancy-interstitial pairs. In contrast to GaAs, where absorption by Ga-H centers increases upon loss of As-H, no absorption attributable to In-H was observed in either InAs or InP. Hydrogen in an As vacancy is the suggested model for Ga-H centers. If such vacancies are thermally unstable in In-based compounds, it would explain an absence of In-H bonds and may reduce the capability for ion implantation to produce electrical isolation in In-based compound semiconductors.
Hydrogen Passivation of Si and Be Dopants in InAlAs
Authors: Roos G. , Johnson N. M. , Pao Y. C. , Harris J. S. , Herring C.y 
Published: March 2011

ABSTRACTHydrogen passivation and thermal reactivation of Si donors and Be acceptors were investigated in In0.52Al0.48As grown by molecular beam epitaxy. The semiconducting alloy was passivated by exposure to monatomic hydrogen or deuterium from a remote microwave plasma. The passivation was achieved by exposing the samples to monatomic hydrogen at temperatures between 200 and 250 °C for 1h. The electrical activity of the dopants was monitored by spreading resistance and C-V measurements. The samples were homogeneously doped to concentrations of 1.5×1016 or 6×1017 Si / cm3 and 6×1017 Be / cm3. Both dopants were passivated by more than two orders of magnitude through the epitaxial layers. An additional annealing step (440°C, 5 min) resulted in a complete reactivation of the passivated dopants. In addition to the electrical measurements, secondary ion mass spectroscopy showed that for both the Be- and the Si-doped layers the hydrogen profiles were essentially identical to the dopant profiles throughout the epilayers. This behaviour suggests that hydrogen migration is a dopant-trapping-limited process in n-and p-type In0.52Al0.48As.
Raman Microprobe Spectroscopy and Photon Scanning Tunneling Spectroscopy: Applications to Optical Waveguides
Authors: Jackson Howard E. 
Published: March 2011

ABSTRACTRecent results from our laboratory on the characterization of optical waveguides are reviewed. In particular, two means of experimental characterization that provide spatially local information are presented. Raman microprobe spectroscopy is used to explore the role of stress in a GaAlAs channel waveguide and to characterize the nature of impurity induced compositional mixing in a multiple quantum well structure suitable for optical waveguiding. Finally, photon tunneling microscopy is shown to probe the optical waveguide evanescent field and thus the local surface and index variations in an optical waveguide.
Trimethylamine Alane for Low-Pressure Movpe Growth of AlGaAs-Based Materials and Device Structures
Authors: Schneider R. P. , Bryan R. P. , Jones E. D. , Biefeld R. M. , Olbright G. R. 
Published: March 2011

ABSTRACTThe use of trimethylamine alane (TMAAl) as an alternative to trimethylaluminum (TMAl) for low-pressure metalorganic vapor-phase epitaxy (MOVPE) of AlGaAs thin films as well as complex optoelectronic device structures has been studied in detail. AlGaAs layers were grown in a horizontal reaction chamber at 20–110 mbar with growth temperatures in the range 650°C≤TG≤750°C. Wafer thickness uniformity is strongly dependent on growth pressure, and is acceptable only for the highest linear flow velocities. The 12K photoluminescence (PL) spectra of AlGaAs layers grown using TMAAl and TEGa exhibit uniformly intense and narrow bound-exciton emission throughout the growth temperature range investigated. To assess the viability of this new source for the low-pressure OMVPE growth of advanced optoelectronic devices, several optically-pumped vertical-cavity surface-emitting laser (VCSEL) structures were grown using TMAAl extensively. Room temperature lasing at 850 nm was reproducibly obtained from the VCSEL structures, with a threshold pumping power comparable to similar structures grown by molecular beam epitaxy in our laboratories.
Zinc Diffusion Rates and Profiles in AlGaAs Alloys
Authors: Smith F. T. J. 
Published: March 2011

ABSTRACTThe diffusion rate of Zn in AlxGa1−xAs alloys has been determined, for values of x up to 1.0, as a function of temperature. At 625°C the diffusion coefficient shows a strong dependence on x, reaching a maximum at about 65% Al. A similar rapid increase in diffusion coefficient with x is seen at 700°C. The zinc concentration profiles are similar for all values of x, showing a very abrupt diffusion front. The activation energy for diffusion decreases with increasing x.
Shubnikov-De Haas Studies of Negative Persistent Photoconductivity in AlGaSb/InAs/AlGaSb Quantum Wells
Authors: Lo Ikai , Mitchel W. C. , Manasreh M. O. , Stutz C. E. , Evans K. R. 
Published: March 2011

ABSTRACTWe have measured the Shubnikov-de Haas (SdH) effect in the MBE grown Al0.6Ga0.4Sb/InAs/Al0.6Ga0.4Sh single quantum well (QW) for the magnetic fields up to 4.5T and the temperatures from 1.1 K to 4.2K. The carrier concentration of the two dimensional electron gas (2DEG) was varied via the negative persistent photoconductivity (NPPC) effect. By illuminating the sample with a red light-emitting diode (LED) at the low temperature, the carrier concentration of the 2DEG in the InAs well was reduced from 5.8×1011 cm−2 to 3.6×1011 cm−2 and the corresponding quantum lifetime increased from 0.16ps to 0.21ps. The effective mass was determined by the temperature dependence of SdH oscillations and equal to (0.0317 ± 0.0005)m0.
Ion Implantation Related Defects in GaAs
Authors: Jones K. S. , Bollong M. , Haynes T. E. , Deal M. D. , Allen E. L. , Robinson H. G. 
Published: March 2011

ABSTRACTExtended defect formation is studied in ion implanted GaAs. A number of different species including Si+, Al+, Mg+, Ge+, As+, and Sn* have been investigated. Cross-sectional TEM studies have been done comparing the as-implanted structure (amorphous or crystalline) with the final defect location and morphology. The defects are identified by the same classification scheme used for implanted and annealed silicon. It is found that the threshold dose for type I defect formation is very sensitive to the implant energy for heavier ion masses. Type II, III and IV defects are unstable at annealing temperatures below 900°C. Type V defects are of a loop morphology for Si* and Ge* implants. The source of the interstitials may be a kickout process as the implanted species moves onto substitutional sites. Type V defects for Sn implants appear as precipitates which at the annealing temperature appear to be migrating in the liquid phase. Upon cooling the Sn precipitates, in many cases, solidify as grey (α) Sn.
Indium-Carbon Co-Implantation in GaAs
Authors: Madok J. H. , Haegel N. M. 
Published: March 2011

ABSTRACTWe report on the formation of p+ layers in GaAs by the co-implantation of indium with carbon. Sheet hole concentrations of 2E14 cm−2 were achieved. The co-implant acts to create stoichiometric disturbances and to increase VAs concentration, allowing the C to occupy the vacant As lattice sites. The effect of In on the stoichiometry of the implanted layer was investigated. It was found that addition of 0.1–1% of a group III ion had the effect of shifting the effective As fraction toward the Ga-rich region, thus altering the crystal stoichiometry.
Impurity Profiles in InP from Ion Implantation at Elevated Temperatures
Authors: Kringhoj P. , Svensson B. G. 
Published: March 2011

ABSTRACTThe chemical profiles of Zn, Ge, and Se implanted into InP at elevated temperatures have been measured with secondary ion mass spectrometry and correlated to the implantation damage as deduced from RBS/channeling measurements. An asymmetric broadening of the chemical profiles towards the bulk was found for implantation temperatures above 150°C. This effect is concluded to be due to impurity channeling during implantation.
Deep Donor and Acceptor Levels Induced by High Temperature and long time Annealing in LEC Gallium Arsenide
Authors: Marrakchi G. , Kalboussi A. , Guillot G. , Ben Salem M. , Maaref H. , Molva E. 
Published: March 2011

ABSTRACTThe effects of high temperature isothermal annealing on the electrical properties of donor and acceptor defects in n-type LEC GaAs are investigated. The annealing experiments are performed under As-rich atmosphere at 1000°C for 1–4 and 16 hours followed by a very quick quenching into cold water of the quartz ampoules containing the samples. The donor and acceptor levels are detected respectively by standard (DLTS) and optical (ODLTS) deep level spectroscopy. DLTS results show the presence of one single donor level present in unannealed and annealed samples at Ec - 0.79eV which is identified as the well known electron trap EL2 Only the sample annealed for 16 hs exhibits the presence of a new electron trap named TAI at Ec - 0.32eV. The appearance of TAI is correlated in one hand with the evolution of EL2 concentration and in the other hand to the effect of long duration (16 hs) of the treatment. For acceptor levels, two hole traps HT1 and HT2 are detected respectively at EV + 0.18 eV and EV+ 0.28 eV. HT1 is detected only in samples annealed for 4 and 16 hs and HT2 is detected in all studied samples. Photoluminescence (PL) measurements show the presence of the 1.44 eV band corresponding to gallium antisite GaAs defect. This band observed in unannealed and annealed samples shows that GaAs remains stable even after thermal annealing at lOOO°C for 16 hs and it is correlated with the presence of HT2.
Oxygen in Gallium Arsenide
Authors: Alt Hans Ch. 
Published: March 2011

ABSTRACTThe influence of oxygen-related defects on the compensation behavior of semi-insulating gallium arsenide has been studied. Off-center substitutional oxygen (Ga-O-Ga center) forms an electrically active defect with two levels in the fundamental gap. The negative-U ordering of these levels is the origin for very unusual electrical and optical properties. By oxygen implantation and annealing high concentrations of this center are created which are technologically useful to obtain high-resistivity surface layers.
Shallow Ion Implantation in Gallium Arsenide Mesfet Technology
Authors: de Souza J. P. , Sadana D. K. 
Published: March 2011

ABSTRACTThis review emphasizes controlled shallow doping of GaAs by ion implantation for state-of-art GaAs IC technology. Electrical activation behavior of Si+ and SiF+ implanted GaAs after RTA under capless and PECVD Si3N4-capped conditions will be compared. It will be demonstrated that a remarkable improvement (> 20 %) both in carrier activation and as well mobility can be achieved by co-implanting low doses (< 1013 cm−2 of Al+ into n-dopant (including Si, Se and Te) implanted GaAs and subsequently annealing the material under capless RTA conditions. The maximum improvement in the electrical results with Al+ co-implants occurs for doses (e.g. < 1013 cm−2 for 30 keV Si+) which are used for fabricating shallow channels for submicron GaAs MESFETs. Complex dopant-annealing environment interactions during a buried p layer formation (using either Mg+ or Be+) will be discussed.
Interface Recombination in III/V Heterostructures Investigated Through the Power Dependence of Excitonic Photoluminescence
Authors: MüLlenborn M. , Haegel N. M. 
Published: March 2011

ABSTRACTPhotoluminescence spectra of AlGaAs/GaAs heterostructures with layer thicknesses in the micrometer range show excitonic recombination peaks from the AlGaAs as well as the GaAs layer. Luminescence in the buried GaAs layer may be produced by charge carrier diffusion across the interface and/or photon recycling. We have monitored the luminescence intensity from both layers as a function of laser power in order to determine the dominant generation process in the GaAs layer. The ambi polar diffusion equation has been solved to derive the charge carrier distribution. Based on these data the relative intensities of the AlGaAs and the GaAs excitonic luminescence can be used to obtain information about the interface recombination in a nondestructive way. This characterization method has been applied to investigate the quality of GaAsP/GaAs interfaces as a function of increasing lattice mismatch and dislocation density.
Surface Acoustic Wave Detection of Large Lattice Relaxation of Metastable EL2 in LT-GaAs
Authors: Khachaturyan Ken , Weber Eicke R. , White Richard M. 
Published: March 2011

ABSTRACTFor the first time, surface acoustic waves (SAWs) were used to study the lattice relaxation of metastable defects. A persistent increase of as much as 0.4% of the SAW velocity at low temperatures was observed after illumination of LT-GaAs; this increase could be quenched by annealing at 120–130°K. This behaviour is caused by the metastable transition of EL2-like AsGa defects and constitutes the direct experimental proof of the illumination induced large lattice relaxation of this defect.
Surface Ordering of MBE Grown 001 Ga1−xAlxAs- A Theoretical Study
Authors: Trivedi Rita , Venkatasubramanian R. 
Published: March 2011

ABSTRACTThe kinetics of MBE growth of Ga1-x.,Alx,As is studied theoretically using the stochastic model of MBE growth based on the master equation approach and the random distribution approximation. The surface ordering phenomenon during the 001 growth of Ga0.5Al0.5 As is investigated as a function of the growth conditions. The atom pair interaction energy parameters for various surface configurations were obtained from the first principle calculations. The other model parameters needed in the description of the kinetic processes are obtained from the available experimental data. The ordering kinetics is studied as a function of fluxes, flux ratio and growth temperature. The degree of ordering is estimated in terms of the short range order parameter. The short range order parameter increases with temperature till 650°K and 750°K for cation to anion flux ratios 2 : 1 and 1 : 5, respectively. Beyond this critical temperature, the short range order parameter decreases. This critical temperature is identified as the kinetic order-disorder temperature. The order-disorder phenomenon observed in this theoretical study is explained in terms of the dependence of the surface migration rate of the cations on the growth temperature. The dependence on the order-disorder temperature on the flux ratio is attributed to decreased surface migration for larger flux ratios.
Electronic and Optoelectronic Applications of Materials Grown at a Low Temperature by MBE
Authors: Mishra U. K. , Kolbas R. M. 
Published: March 2011

ABSTRACTMaterials grown at a low temperature by MBE and subsequently annealed at a high temperature have an excess amount of Arsenic and have demonstrated high dielectric breakdown strength and low carrier lifetime. These properties have found applications in analog and switching power applications, in picosecond pulse generation, in device isolation and in the selective intermixing of heterostructures. This paper reviews these applications.
Ultrafast Properties and Applications of GaAs and InP Based Materials Grown by MBE at Low Temperatures
Authors: Gupta S. , Mourou G. , Smith F. W. , Calawa A. R. 
Published: March 2011

ABSTRACTThe ultrafast carrier dynamics in GaAs, In0.52Al0 48As on InP, and In0.53Ga0.47As on InP, grown by molecular-beam-epitaxy (MBE) at low substrate temperatures, are investigated. A reduction in the carrier lifetime is observed with decreasing growth temperatures. The shortest carrier lifetimes of typically a picosecond (ps) are obtained at the lowest growth temperature range of 150 – 200 'C. Femtosecond optical absorption and reflectance measurements have been used to verify the sub-picosecond carrier lifetimes. Photoconductive switching measurements on these materials, measured using the technique of electro-optic sampling have further confirmed the sub-picosecond carrier lifetimes, and have also resulted in the generation of subpicosecond electrical signals. These short electrical pulses have been used for a variety of ultrafast optoelectronic applications.
Characterization of Electrical Properties of Low Temperature GaAs
Authors: Wu Bin , Verma Ashish , Gamelin John , Sohn Hyunchul , Wang Shyh 
Published: March 2011

ABSTRACTLT GaAs(220°C) was grown on an n+ substrate and capped with n+ GaAs grown at 600°C (n-i-n). Complete IV and CV measurements were performed. The IV characteristics exhibit ohmic, trap-filling and space-charge-limited regimes. We have developed a model based upon the compensation of background shallow acceptors by deep donor traps, large concentrations of which have been shown to exist in LT GaAs. Computer simulation of the IV curve is compared with experimental results. The “breakdown” is attributed to trapfilling under electron injection. It is also found that when the voltage across the structure is changed, the current takes several seconds to reach steady state. This is consistent with our model, which assumes slow trapping and detrapping in the LT GaAs. High frequency CV measurements show the capacitance to be fairly constant for voltages below “breakdown”.
Study of Deep Levels in LT-GaAs Materials and SI-GaAs Wafers by an Improved Thermoelectric Effect Spectroscopy
Authors: Huang Z. C. , Wie C. R. 
Published: March 2011

ABSTRACTWe have developed a simpler and more reliable method of thermoelectric effect spectroscopy (TEES) by eliminating the second heater in the technique. We have applied this method to the deep level studies in semi-insulating(SI) GaAs epitaxial layers grown at a low temperature by molecular beam epitaxy (LT-GaAs) and SI-undoped GaAs, Cr-doped GaAs. We have found that the electrical contacts on front and back surfaces of the sample are more reliable for the TEES measurement than both contacts made on the same surface. In this contact arrangement, the temperature difference of about 1–2K between the back and front surfaces was enough to produce a clear and reliable TEES data, without the need for a second heater. The results obtained by TEES are consistent with the results obtained by photo-induced current transient spectroscopy (PICTS) and by thermally stimulated current (TSC) measurements. The TEES results clearly distinguish between the electron traps and the hole traps. We will discuss the results on the various semi-insulating GaAs samples and the advantages and limitations of the TEES technique.
The Modification of the Abrasion Resistance of Type IIa (110) Diamond Using Carbon and Nitrogen Implantation
Authors: Anderson Gregory C. , Prawer Steven , Johnston Peter N. 
Published: March 2011

ABSTRACTThe modification of the wear properties of type Ha diamond following ion implantation with 100 keV carbon and nitrogen has been studied at implantation temperatures of 150 and 470 K. Abrasion testing using low load multiple pass scratch testing with a Rockwell diamond indenter has shown a decrease in wear resistance. Microstructural modifications resulting from ion implantation have been assessed using Channeling Rutherford Backscattering Spectroscopy (C-RBS). No correlation was found between the presence of ion beam induced point defects (as measured by C-RBS) and the increase in wear. There are no obvious wear rate differences observed for nitrogen or carbon implantation.
The Mbe Growth of Widegap II-VI Injection Lasers and LEDs
Authors: Xie W. , Grillo D.C. , Kobayashi M. , Gunshor R. L. , Jeon H. , Ding J. , Nurmikko A. V. , Hua G. C. , Otsuka N. 
Published: March 2011

ABSTRACTStriking progress in the development of II-VI semiconductor heterostructures, coupled with seminal advances in doping, has very recently led to the first demonstration of blue and blue/green diode lasers operating from cryogenic to room temperature. The active region in these devices was based on the (Zn, Cd)Se/ZnSe multiple quantum wells (MQW) which had earlier been actively studied as a candidate for laser medium by optical pumping techniques. We report on the performance of such MQW diode lasers with emphasis on structural versatility in terms of preparation on both p-type and n-type GaAs substrates, and where sulfur is or is not incorporated for blue/green color lasing. In this work we have obtained pulsed, high power, high quantum efficiency laser emission up to near room temperature conditions. Efficient LED devices are described which operate in the blue (494nm) at room temperature.
Alloy Dependent Properties of Excitons and Deep Acceptors in CdZnTe Volume Crystals
Authors: Meyer B. K. , Hofmann D. M. , Oettinger K. , Stadler W. , Efros Al. L. , Salk M. , Benz K. W. 
Published: March 2011

ABSTRACTCd1-xZnxTe ZriTe crystals grown by the travelling heater methode (THM) have been investigated by low temperature photoluminescence (PL). The excitonic energy gap as a function of the alloy composition was determined for the complete range of x - 0 to x - 1. The composition dependent broadening of the neutral acceptor bound exciton (A°X) line was measured and compared to theoretical calculations. The Donor - Acceptor pair luminescence in the crystals is a superposition of recombinations due to residual Cu acceptors and A - centers (anion vacancy - donor pairs ).
Growth of Epitaxial ZnS Films by Pulsed-Laser Ablation
Authors: McCamy J. W. , Lowndes D. H. , Budai J. D. , Chakoumakos B. C. , Zuhr R. A. 
Published: March 2011

ABSTRACTPulsed KrF (248nm) laser ablation of a polycrystailine ZnS target has been used to grow high quality, carbon-free, epitaxial ZnS thin films on GaAs(OOl), GaAs(111), and GaP(OOl). The films were grown at temperatures of 150–450°C, using a rotating substrate heater and deposition geometry that produces films with highly uniform thickness. X-ray rocking curves are consistent with (111) stacking faults being the dominant defects in the ZnS films grown on GaAs. The estimated stacking fault density is ∼6 × 1010 cm-3, comparable to the best MOCVD ZnS films. RBS analysis shows that these defects are located predominantly near the GaAs-ZnS interface. The anisotropy of the ZnS growth rate, between the GaAs(001) and GaAs(111) surfaces, was found to be temperature-dependent.