bluuebunny/crossref_metadata_2025_split huggingface dataset:
Raman and Photoluminescence Mapping of Lattice Matched InGaP/GaAs Heterostructures
Authors: Attolini G. , Fallini P. , Germini F. , Pelosi C. , Martínez O. , Sanz L. F. , González M. A. , Jiménez J. 
Published: April 2011

AbstractThe influence of the substrate on composition and CuPt-type spontaneous order of MOVPE lattice matched InGaP/GaAs layers was studied. The study was carried out by microRaman and microphotoluminescence. The order was determined by the band gap, while the Raman parameters were also contributed by the surface topography that was also related to the type of substrate. The spontaneous order increases with Si- doping of the substrates. Doping the layers with Zn randomises the alloy.
InAsN Grown by Plasma-Assisted Gas Source MBE
Authors: Shih Ding-Kang , Lin Hao-Hsiung , Chu Tso-Yu , Yang T. R. 
Published: April 2011

AbstractWe report the structural, electrical and optical properties of bulk InAsN alloy with various nitrogen contents deposited on (100) InP substrates by using plasma-assisted gas source molecular beam epitaxy. It is found that the fundamental absorption edge of InAsN, as compared to that of InAs, shifts to higher energy due to Burstein-Moss effect. A dramatic increase of the electron effective mass in a nitrogen-containing III-V alloy is also observed from infrared reflectivity and Hall measurement on these degenerate InAsN samples. The sizeable increase on electron effective mass is consistent with the theoretical predictions based on band-anticrossing model.
Deep Centers and Their Capture Barriers in MOCVD-Grown GaN
Authors: Johnstonea Daniel K. , Ahoujjab Mohamed , Yeoc Yung Kee , Hengeholdc Robert L. , Guidod Louis 
Published: April 2011

AbstractGaN and its related alloys are being widely developed for blue-ultraviolet emitting and detection devices as well as high temperature, high power, and high frequency electronics. Despite the fast improvement in the growth of good quality GaN, a high concentration of deep level defects of yet unconfirmed origins are still found in GaN. For both optical and electronic devices, these deep carrier traps and/or recombination centers are very important and must therefore be understood. In the present work, deep level defects in GaN grown on sapphire substrates by metal organic chemical vapor deposition (MOCVD) have been investigated using Isothermal Capacitance Transient Spectroscopy (ICTS) and Current Voltage Temperature (IVT) measurements. Several deep level electron traps were characterized, obtaining the emission energy, concentration, and capture cross section from a fit of exponentials to the capacitance transients. ICTS was also used to reveal information about the capture kinetics involved in the traps found in GaN by measuring the amplitude of the capacitance transient at each temperature. At a reduced filling pulse where the traps were not saturated, several of them showed marked reduction in capacitance transient amplitude when compared to the transient amplitude measured under conditions where the filling pulse saturates the traps. This reduction in transient amplitude indicates that there is a barrier to carrier capture, in addition to the emission barrier. It has been found that several traps had capture barriers that were significant fractions of the emission energies up to 0.32 eV. These capture barriers may lead to persistent photoconductivity and reduced trapping. In this paper, deep level emission energies as well as capture barrier energies found in MOCVD-grown GAN will be discussed.
Quantum Dot Long-Wavelength Detectors
Authors: Bhattacharya Pallab , Stiff-Roberts Adrienne D. , Krishna Sanjay , Kennerly Steve 
Published: April 2011

AbstractLong-wavelength infrared detectors operating at elevated temperatures are critical for imaging applications. InAs/GaAs quantum dots are an important material for the design and fabrication of high-temperature infrared photodetectors. Quantum dot infrared photodetectors allow normal-incidence operation, in addition to low dark currents and multispectral response. The long intersubband relaxation time of electrons in quantum dots improves the responsivity of the detectors, contributing to better hightemperature performance. We have obtained extremely low dark currents (Idark = 1.7 pA, T = 100 K, Vbias = 0.1 V), high detectivities (D* = 2.9×108cmHz1/2/W, T = 100 K, Vbias = 0.2 V), and high operating temperatures (T = 150 K) for these quantum-dot detectors. These results, as well as infrared imaging with QDIPs, will be described and discussed.
A Theoretical Study of Structural Disorder and Photoluminescence Linewidth in InGaAs/GaAs Self Assembled Quantum Dots
Authors: Lin Yih-Yin , Jiang Hongtao , Singh Jasprit 
Published: April 2011

AbstractThe past few years have seen considerable efforts in growth and device application of selfassembled quantum dots. However, the photoluminescence (PL) linewidth, which represents structural fluctuations in dot sizes, is still in the range of 30–50 meV. This large linewidth has deleterious effects on devices such as lasers based on self-assembled dots. In this paper we will examine the configuration-energy diagram of self-assembled dots. Our formalism is based on: (1) an atomistic Monte Carlo method which allows us to find the minimum energy configuration and strain tensors as well as intermediate configurations of dots; (2) an 8-band k·p method to calculate the electronic spectra. We present results on the strain energy per unit cell for various distributions of InAs/GaAs quantum dots and relate them to published experimental results. In particular we examine uncovered InAs/GaAs dots and show that in the uncovered state a welldefined minimum exists in the configuration energy plot. The minimum corresponds to the size that agrees well with experiments.
PbTe Flash Evaporation on Si <100> Substrates for Heterojunction Infrared Detectors
Authors: Guimarães Sonia , Silva Sabrina de C. F. F. da , Assis João M. K. de 
Published: April 2011

AbstractThis work is to present results of flash evaporation of PbTe directly over single crystals p-type Si substrates, in order to produce heterojunction infrared detectors (HIRD), working at 4.3μm IR wavelength. The evaporation was performed on modified JEOL vacuum equipment, model JEE4B(a), working with vacuum pressure around 10−5 torr, using diffusion pump. The HIRDs produced with this method presented the same detectivity (D*) values of HIRDs made with Hot Wall Epitaxial System (HWE)(b), in which PbTe epitaxial layers were grown directly over the same Si substrates, where an ionic pump reached about 10−7 torr as vacuum pressure. The best results, were obtained with PbTe layers grown with Molecular Beam Epitaxial (MBE) method(c) directly over Si substrates, where the vacuum pressure is around 10−9 torr, also using an ionic pump. The advantage of growing PbTe directly over Si wafers is that the HIRDs perform at room temperature. The detectivity values of HIRDs obtained with methods (a) and (b), were D*≈4,8 × 105 cm.Hz1/2 W−1 and with method (c), D* ≈ 6,7 × 106 cm.Hz1/2 W−1. Different technologies: (a) very low costs, (c) high technology; not very different results.
Calculations of Dielectric Constant for AlGaInAs Quaternary Semiconductor Alloy in the Transparent Region and Above (0.4-4.0eV)
Authors: Linnik M. , Christou A. 
Published: April 2011

AbstractThe modeling of the spectral behavior of the refractive index of AlGaInAs quaternary IIIV semiconductor alloy in the energy range from 0.4 to 4eV, including the transparent region, is presented. The extended model of interband transition contributions incorporates not only the fundamental absorption edge contribution to the dielectric function, but also contributions from higher energy and indirect transitions. It is demonstrated that indirect energy transitions must be included in the calculations of the complex dielectric function of the material in the transparent region. Indirect transitions from different critical points in the Brillouin zone are treated separately. The comparison between the theoretical refractive indices and the experimental data for AlGaInAs alloy is presented. These calculations have been applied to the design of Bragg mirrors with the highest refractive index contrast for heterostructure lasers.
Annealing of some II-IV-V2 crystals in the vapor of volatile constituents
Authors: Voevodin Valeriy G. , Voevodina Olga V. , Bereznaya Svetlana A. , Korotchenko Zoya V. , Fernelius Nils C. , Goldstein Jonathan T. , Ohmer Melvin C. 
Published: April 2011

AbstractExperiments on annealing of CdGeAs2-, CdSnAs2- and ZnGeP2-crystals in the vapor of volatile constituents were carried out. Conductivity and Hall effect measurements were performed to characterize the modification of electrical properties, caused by the interaction of the crystal with the gas phase during annealing. Literature data and the results of the present work are discussed based on the results of a quasi-chemical analysis. This yielded that the results of annealing depends essentially on both the conditions of the experiment and the initial imperfection of the crystal. The most probable native structural defects becoming apparent under the annealing were the following: for CdSnAs2 - SnCd, VAs; for CdGeAs2 - VAs, VCd, CdGe, GeCd; for CdSiAs2 - SiAs, VAs ; for CdSiP2 - VCd, VP; for ZnGeP2 - ZnGe, GeZn, VZn, VP; and for ZnSnP2- ZnSn, SnZn, VZn, VP.
Annealing effect on the nonradiative carrier recombination in AlGaAs/GaAs investigated by a piezoelectric photothermal spectroscopy
Authors: Fukuyama Atsuhiko , Nagatomo Hiroaki , Akashi Yoshito , Ikari Tetsuo 
Published: April 2011

AbstractElectron non-radiative recombination process of photoexcited carriers in as-grown and annealed n-Al0.2Ga0.8As/GaAs hetero-structure samples are investigated by using a piezoelectric photothermal spectroscopy (PPTS). The PPT signal above the band-gap energy of GaAs substrate decreased when the sample was annealed at 815°C. In the frequency dependent measurements, the deviations from 1/f linear function are clearly observed in the AlGaAs/GaAs samples. This critical deviation frequency was found to shift to the lower frequency region by annealing. Our experimental results are explained by assuming that the sample annealing generates an unknown deep level in AlGaAs epitaxial layer region and this level effectively traps the photoexcited carriers non-radiatively.
On the scaling of exciton and impurity binding energies and the virial theorem in semiconductor quantum wells and quantum-well wires
Authors: Leyva-Dios M. de , Oliveira L. E. 
Published: April 2011

AbstractWe have used the variational and fractional-dimensional space approaches in a study of the virial theorem value and scaling of the shallow-donor binding energies versus donor Bohr radiusin GaAs-(Ga,Al)As semiconductor quantum wells and quantum-well wires. A comparison is made with previous results with respect to exciton states. In the case the donor ground-state wave function may be approximated by a D-dimensional hydrogenic wave function, the virial theorem value equals 2 and the scaling rule for the donor binding energy versus quantum-sized Bohr radius is hyperbolic, both for quantum wells and wires. In contrast, calculations within the variational scheme show that the scaling of the donor binding energies with quantum-sized Bohr radius is in general nonhyperbolic and that the virial theorem value is nonconstant.
Luminescence of quasi-2DEG in heterostructures based on PbS films
Authors: Khlyap G. 
Published: April 2011

AbstractThe paper deals with the problem of luminescence due to non-equilibrium charge carriers transfer between the quasi-2D electron system localized in the space-charge region of the heterostructures based on lead sulfide films (up to 3 μm thickness) and zinc selenide substrates surrounded by the wide gap semiconductor region. The processes of electro- and photoluminescence are studied, the band diagram is proposed and the main parameters of the structure PbS/quasi-2DEG/ZnSe are calculated.
Optical Characterization of Iv-VI Mid-Infrared Vcsel
Authors: Zhao F. , Wu H. , Zheng T. , McCann P. J. , Majumdar A. , Jayasinghe Lalith , Shi Z. 
Published: April 2011

AbstractPbSe/PbSrSe multiple-quantum-well (MQW) structures and PbSrSe thin films were grown on BaF2 (111) substrates by molecular beam epitaxy (MBE) and characterized by Fourier transform infrared (FTIR) spectrometer. Strong photoluminescence without Fabry-Perot interference fringes was observed even at room temperature from the MQW structures. The peak energies for the MQW structures with different well widths shifted to high energy with increasing temperature. The absorption edge of PbSrSe layer was determined by transmission spectra. Meanwhile, we designed and fabricated λ=4.1 μm MQW vertical cavity surface emitting laser (VCSEL). A power output of 40 mW was obtained at room temperature. The room temperature threshold pump density is 200 kW/cm2.
Sb-Based Mid-Infrared Diode Lasers
Authors: Mermelstein C. , Rattunde M. , Schmitz J. , Simanowski S. , Kiefer R. , Walther M. , Wagner J. 
Published: April 2011

AbstractIn this paper we review recent progress achieved in our development of type-I GaInAsSb/AlGaAsSb quantum-well (QW) lasers with emission wavelength in the 1.74–2.34 μm range. Triple-QW (3-QW) and single-QW (SQW) diode lasers having broadened waveguide design emitting around 2.26 μm have been studied in particular. Comparing the two designs we have find that the threshold current density at infinite cavity length as well as the transparency current density scale with the number of QWs. Maximum cw operating temperature exceeding 50°C and 90°C has been obtained for ridge waveguide lasers emitting above and below 2 μm, respectively. Ridge waveguide diode lasers emitting at 1.94 μm exhibited internal quantum efficiencies in excess of 77%, internal losses of 6 cm−1, and threshold current density at infinite cavity length as low as 121 A/cm2 reflecting the superior quality of our diode lasers, all values recorded at 280 K. A high characteristic temperature TOof 179 K for the threshold current along with a value of T1 = 433 K for the characteristic temperature of the external efficiency have been attained for the 240–280 K temperature interval. Room temperature cw output powers exceeding 1.7 W have been demonstrated for broad area single element devices with highreflection/ antireflection coated mirror facets, mounted epi-side down. The latter result is a proof for the high power capabilities of these GaSb-based mid-ir diode lasers.
Field Effect Controlled Photoresistors Based on Chemically Deposited PbS Films
Authors: Pentia Eugenia , Pintilie Lucian , Matei Ion , Pintilie Ioana 
Published: April 2011

AbstractMOS-like structures were obtained by chemical deposition of a polycrystalline PbS thin film on top of a silicon dioxide/Si substrate. Gold ohmic electrodes in coplanar configuration were subsequently deposited by vacuum evaporation on PbS surface (drain and source electrodes). The gate aluminum electrode was deposited on the back of the Si substrate. The dependence of the photoconductive signal, generated in the PbS film, on the gate voltage was studied for wavelengths ranging between 800 nm and 3000 nm at room temperature as well as at low temperatures. It was found that the relative variation of the signal could be as high as 50 % for gate voltages ranging between −30 V and +30 V. Two possible mechanisms are proposed to explain the signal variation with the gate voltage: 1) Variation of the depleted region's thickness in the PbS film, that leads to a variation of the conduction channel's resistance (the reference resistance called, also, the dark resistance), 2) The possible variation of the majority carriers (holes) life-time due to the electron blocking at the PbS/oxide interface when positive gate voltages are applied on the back electrode. Integrated IR detectors with controlled sensitivity in the 800–3000 nm range can be manufactured at a relatively low cost using the PbS/oxide/Si MOS-like structure.
Photo-stimulated Rebuilding of Structure in Semiconductors
Authors: Rashidova S. S. , Oksengendler B. L. , Turaeva N. N. , Aripov I. M. 
Published: April 2011

AbstractA strong electron-phonon interaction observed in semiconductors allows to realize a special kind of atomic rebuilding under photo-irradiation of the medium. We consider three types of defective structures: one atomic, two-atomic (“dump-bell”) and multi-atomic (kinks) defects. It is shown that an inversion effect of the defect potential term may be realized if there are non-equivalent neighboring positions of one-atomic and two-atomic defects. In this case the photo-excitation of electronic subsystems of these defects leads to an inversion of potential terms and a consecutive athermal rebuilding of the defective structures. The Yahn-Teller effect and psevdo-effect play a special role here. It is shown for kink-structures that the photo-excitation of the electronic subsystems results in the alteration of kink nonius and the successive exponentially strong decrease of an activation barrier. Especially effects of athermal atomic rebuilding of U-negative defects are considerable.
Effect of Zn atom diffusion in the active layer of InGaAlP visible-LED investigated by the Piezoelectric Photothermal Spectroscopy
Authors: Ohno Ryuji , Taiji Yoshihito , Sato Shoichro , Fukuyama Atsuhiko , Shigetomi Shigeru , Ikari Tetsuo 
Published: April 2011

AbstractIt has been reported that Zn atoms diffused from the Zn-doped p-InAlP cladding to the active layer in InGaAlP visible-light-emitting diodes cause a degradation of light output efficiency. A doping effect of the Zn atoms was then investigated using a Piezoelectric Photothermal Spectroscopy from a nonradiative transition point of view. The results indicate that the Zn-doping unexpectedly induces a decrease of the nonradiative component of the electron transitions above the band gap of the active layer. The experimental results are explained by considering that Zn doping cause the increase of both shallow and deep acceptor levels at the same time with the different rate for generation.
CVD Diamond Thin Films for Alpha Particle Detector Application
Authors: Wang S. G. , Zhang Q. , Yoon S. F. , Ahn J. 
Published: April 2011

AbstractIn this paper, CVD diamond thin films for alpha particle detector have been prepared using hot-filament chemical vapor deposition (HFCVD) technique. Alpha particle detectors with coplanar and sandwich electrode geometry have been fabricated on the diamond films using liftoff technology. The detector performance has been tested using a 241 Am source with a characteristic energy of 5.5 MeV. An average charge collection efficiency of 32 % for the detector with coplanar and of 21 % for the detector with sandwich geometry is obtained.
Improved Routes towards Solution Deposition of Indium Sulfide Thin Films for Photovoltaic Applications:
Authors: Govender Kuveshni , Smyth-Boyle David , O'Brien Paul 
Published: April 2011

AbstractConditions necessary for the reproducible deposition of pristine In2S3 thin films on TO-glass substrates by low temperature solution deposition have been identified. Baths containing carboxylic acids yield adherent, specular and crystalline films, within a defined pH range, dependent on the particular acid employed. Films have been characterised by XRD, SEM, XPS and electronic spectroscopy. As–deposited films were found to crystallise as tetragonal β-In2S3, no evidence for incorporation of hydroxy-indium species was found by XPS measurements.
Properties of 2D and 3D Dielectric Structures Fabricated by Electrochemical Dissolution of III-V Compounds
Authors: Tiginyanu I.M. , Langa S. , Christophersen M. , Carstensen J. , Sergentu V. , Foca E. , Rios O. , Föll H. 
Published: April 2011

AbstractPorous layers and membranes representing 2D and 3D dielectric structures were fabricated on different III-V compounds (GaAs, InP, GaP) by electrochemical etching techniques. Nonlithographically fabricated ordered nanopore arrays in InP are reported for the first time. We show that the reflectance from nanostructured InP is lower than that from bulk InP in the spectral interval 1.5–2.2 eV. The artificial anisotropy induced by nanotexturization was studied in porous GaP membranes and the refractive indices for ordinary and extraordinary beams were evaluated.
Current spreading in AlGaN:Mg cladding layers of laser structures
Authors: Figge Stephan , Böttcher Tim , Zellweger Christoph , Ilegems Marc , Hommel Detlef 
Published: April 2011

AbstractThe consequences of the anisotropic resistance in AlGaN/GaN strained layer superlattices for the operation of laser diodes were studied for structures driven in LED mode. A series of laser structures containing different Mg-doped AlGaN bulk and AlGaN/GaN strained layer superlattice cladding layers was compared to estimate the current spreading in the cladding due to the formation of 2D-hole gases. Current-voltage measurements revealed a significant spread of the current path in the superlattices, whereas no spreading was seen for the bulk cladding. In contrast to this, investigations of the electroluminescence showed no significant differences.
Electrical Characterization of GaN Metal Oxide Semiconductor Diodes Using MgO as the Gate Oxide
Authors: Kim J. , Gila B. P. , Mehandru R. , Johnson J.W. , Shin J. H. , Lee K.P. , Luo B. , Onstine A. , Abernathy C. R. , Pearton S.J. , Ren F. 
Published: April 2011

AbstractGaN metal oxide semiconductor diodes were demonstrated utilizing MgO as the gate oxide. MgO was grown at 100°C on MOCVD grown n-GaN in a molecular beam epitaxy system using a Mg elemental source and an electron cyclotron resonance oxygen plasma. H3PO4 based wet-chemical etchant was used to remove MgO to expose the underlying n-GaN for ohmic metal deposition. Electron deposited Ti/Al/Pt/Au and Pt/Au were utilized as ohmic and gate metallization, respectively. An interface trap density of low-to-mid 1011 eV-1cm-2was obtained from temperature conductance-voltage measurements. Terman method was also used to estimate the interface trap density and a slight lower number was obtained as compared to the conductance method. Results from elevated temperature (up to 300°C) conductance measurements showed an interface state density roughly three times higher(6x1011 eV–1 cm-2 ) than at 25°C.
Proton Irradiation Effects on Scandium Oxide/Gallium Nitride MOS Diodes
Authors: Allums K. , Luo B. , Mehandru R. , Gila B. P. , Dwivedi R. , Fogarty T.N. , Wilkins R. , Abernathy C. R. , Ren F. , Pearton S. J. 
Published: April 2011

AbstractThe stability to proton radiation of GaN metal oxide semiconductor (MOS) diodes fabricated using the novel gate dielectric Sc2O3 was investigated. The MOS diodes were fabricated by depositing the dielectric with molecular beam epitaxy onto MOCVD-grown GaN on sapphire. The stability of GaN Schottky diodes was also investigated for comparison. Current-voltage (I-V) and capacitance-voltage (C-V), were employed to monitor any change in the electrical characteristics of the diodes. Preliminary testing indicates that the GaN-based diodes are in fact affected by proton irradiation, but only at fairly high doses. Doses equivalent to 10 years in low earth orbit, ~5x109cm-2, produce a decrease in the reverse breakdown field in both Schottky and MOS diodes. However, even after irradiation, the GaN MOS diodes showed twice the reverse breakdown voltage of non-irradiated Schottky diodes. Further, while the Schottky diodes showed reduced forward breakdown voltage, the MOS diodes showed no change in forward breakdown. These results suggest that the oxide/GaN interface is stable and is not being damaged by the radiation. The change in reverse breakdown is most likely due to generation of damage in the GaN resulting in the formation of shallow donors.