bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Potential of Hydrogenated Amorphous Silicon-Sulfur Alloys for Absorber Materials in Photovoltaic Devices
Authors: Taylor P. C. , Wang S. L. 
Published: April 2011

AbstractThe group VI element, sulfur, is an inefficient donor in hydrogenated amorphous silicon (a-Si:H). The compensation by sulfur donors of the p-type conductivity obtained with diborane in a-Si:H provides additional evidence of the role of sulfur as a donor. By adding equal amounts of diborane and hydrogen sulfide in the plasma the dark conductivity at room temperature can be reduced by one to two orders of magnitude compared to the corresponding p-type a-Si:H with the same boron concentration. Unlike phosphorus doping, a portion of the sulfur-related donors is passivated by hydrogen in the annealed state. This passivated portion can be rendered electrically active by optical excitation. This effect is similar to that which has been called persistent photoconductivity (PPC) and occurs in some compensated samples of a-Si:H and in some multilayer structures. The PPC effect has the opposite effect on both the photo- and dark conductivities from the Staebler-Wronski effect. For this reason it is possible to find an appropriate S/Si ratio where the two effects cancel as far as the conductivity is concerned. For an appropriate concentration of S in “intrinsic” a-Si:H one can obtain samples with high photoconductivity and essentially no degradation in either the dark or the photo-conductivities upon prolonged optical excitation (light soaking). These results suggest that at least the majority carriers are unaffected; however, it remains unclear what effect this second metastability will have on the minority carriers, and hence on PV device applications. The general idea that the addition of a second metastability to hydrogenated amorphous silicon (a-Si:H) might counteract the deleterious consequences of the Staebler-Wronski effect is presented.
3D Arrays of Quantum Dots for Laser Applications
Authors: Ledentsov N.N. , Böhrer J. , Bimberg D. , Zaitsev S.V. , Ustinov V.M. , Egorov A.YU. , Zhukov A.E. , Maximov M.V. , Kop'ev P.S. , Alferov ZH.I. , Kosogov A.O. , Gösele U. , Ruvimov S.S. 
Published: April 2011

AbstractWe have fabricated and studied injection lasers based on vertically coupled quantum dots (VECODs). VECODs are self-organized during alternate short-period GaAs-InAs (InGaAs) depositions after InAs (or InGaAs) pyramids are formed on a GaAs (100). The resulting arrangement represents laterally ordered array of nanoscale structures inserted in a GaAs matrix, where each structure is composed of several vertically merging InAs (or InGaAs) parts. VECODs are introduced in the active region of GaAs-AlGaAs double heterostructure laser. The threshold current density remarkably decreases with increase in number of periods (N) of the VECOD (down to 90 A cm-2 at 300K for N=10). The differential efficiency increases with N and the lasing occurs through ground state of quantum dot exciton up to room temperature (λ=1.05 μm).
Synthesis of GaAs Nano-Particles by Digital rf-sputtering
Authors: Hirasawa M. , Ichikawa N. , Egashira Y. , Komiyama H. 
Published: April 2011

AbstractNanometer-sized GaAs particles embedded in SiO2 were prepared by a digital rf-sputtering method, where GaAs and SiO2 targets were alternately sputtered in an Ar atmosphere. The GaAs deposition time was kept shorter than the time required to form a continuous layer. Transmission electron microscopy (TEM) observations showed that the sizes of the GaAs particles can be controlled from 2 to 8 nm by changing the sputtering cycle time of the GaAs target. In spite of their small size, the GaAs particles have crystallinity similar to the target material without substrate heating or post annealing. It was also revealed that the mechanism of the particle growth depend on the surface migration of the precursors. The optical absorption spectra of the GaAs particles show a blue shift as large as 1.6 eV, corresponding to strong quantum confinement of electrons and holes.
Photoluminescence Study of Chloride Vpe-Grown Gan
Authors: Ueda Tetsuzo , Yuri Masaaki , Lee Heon , Harris James S. , Baba Takaaki 
Published: April 2011

AbstractWe have examined the effect of growth conditions on photoluminescence (PL) characteristics of chloride VPE-grown GaN films. Undoped GaN films are grown on sapphire by a newly developed chloride VPE system which utilizes GaCl3 and NH3 as source materials.We find that the spectra depend strongly on the growth temperatures and the corresponding surface morphology. Peaks from excitons and donor-acceptor pairs (D-A pair) recombination are observed for the films with terrace-like flat surfaces grown at between 950°C and 1000°C. A peak due to exciton bound to neutral donors is observed for a growth temperature of 975°C where the acceptor-related peaks are not seen. Decreasing the growth temperature below 950°C causes rough surfaces due to three-dimensional growth, whereas increasing the growth temperature above 1000°C causes cracks or partial pealing off of the film. The films with rough surfaces or crystal failures show broad emission from deep acceptor levels. As a result, residual acceptors are eliminated in the very narrow range of the growth temperature around 975°C. It is also noted that an increase of the V/III ratio during the growth makes the line width of the band-edge peak narrower. The PL results show that a growth temperature around 975°C and high V/III ratio are essential to obtain better crystal quality and reduced concentration of residual acceptors.
Vapor Phase Epitaxy of GaN Using Gallium Tri-Chloride and Ammonia
Authors: Yuri M. , Ueda T. , Lee H. , Itoh K. , Baba T. , Harris J.S. 
Published: April 2011

AbstractGaN films with good crystalline quality are grown on sapphire by atmospheric pressure vapor phase epitaxy using gallium tri-chloride (GaCl3) and ammonia (NH3). Epitaxial growth is carried out over temperature and V/III-ratio ranges of 800–1000°C and 100–1000, respectively. Typical growth rate obtained is in the range of 5–20 μm/hr. The films grown below 925°C typically show three dimensional (island) growth, while above that temperature, continuous films are obtained. Films grown at 975°C with a V/III ratio > 300 exhibit a smooth surface. XRD analysis shows that the films are single crystal with hexagonal polytype. Strong band-edge photoluminescence is observed with a FWHM of 60 meV at room temperature and 25 meV at 77K. The results indicate that this simple growth technique is effective for growing high quality bulk GaN, which can be used as a substrate for subsequent epitaxy. In order to further improve the surface morphology, a preliminary experiment on GaN growth on a thin GaN buffer layer prepared by gas source MBE is also presented.
Characterization of the Solid-Phase Epitaxial Growth of Amorphized Gaas with In-Situ Electron Microscopy
Authors: Belay K. B. , Ridgway M. C. , Llewellyn D. J. 
Published: April 2011

AbstractThe influence of non-stoichiometry on the solid-phase epitaxial growth of amorphized GaAs has been studied with in-situ Transmission Electron Microscopy (TEM). Ion-implantation has been used to produce microscopic non-stoichiometry via Ga and As implants and macroscopic non-stoichiometry via Ga or As implants. It has been demonstrated that amorphous GaAs recrystallizes into a thin single-crystal layer and a thick heavily twinned layer. Video images of the recrystallization process have been quantified for the first time to study the velocity of the crystalline/amorphous (c/a)-interface as a function of depth and ion species. Regrowth rates of the single crystal and twinned layers as functions of non-stoichiometry have been calculated. The phase transformation is rapid in Ga-rich material. In-situ TEM results are consistent with conventional in-situ Time Resolved Reflectivity, ex-situ Rutherford Backscattering Spectroscopy and Channelling measurements and ex-situ TEM.
Damage Introduction in Ingap and Aigaas by Electron Cyclotron Resonance ar Plasmas
Authors: Lee J. W. , Pearton S. J. , Stradtmann R. R. , Abernathy C. R. , Hobson W. S. , Ren F. 
Published: April 2011

AbstractChanges in sheet resistance of n- and p-type InGaP exposed to Electron Cyclotron Resonance Ar plasmas have been used to measure the introduction of ion-induced damage. P-type material is much more resistant to change in its conductivity than n-type InGaP, indicating that electron traps are the predominant entity produced by the ion bombardment. For short (˜1 min.) plasma exposures the ion current is more important than ion energy in producing resistance changes. Annealing of damage in both conductivity types occurs with an activation energy of ˜3.4±0.5eV. p+A1GaAs is found to be much more susceptible than n+AlGaAs to the introduction of electrically active deep levels during exposure to Electron Cyclotron Resonance Ar plasmas. In both AlGaAs materials the resistivity of thin (˜0.5μm) epitaxial layers increases rapidly with both plasma exposure time and the ion energy, while the ion density in the Ar discharge has a much greater influence on p+AlGaAs than n-type material. These results suggest that the energetic ion bombardment introduces deep hole traps more readily than deep electron traps in AlGaAs and that pnp transistor structures will be more susceptible to plasma damage than comparable npn structures.
Formation of New Semiconducting Ge-Si-Fe Alloy on Si(100) and its Optical Properties
Authors: Chen H. , Han P. , Huang X.D. , Hu L.Q. , Shi Y. , Zheng Y.D. 
Published: April 2011

AbstractWe report a new semiconducting Ge-Si-Fe alloy thin film grown on Si(100) by reactive deposition epitaxy(RDE) using high vacuum evaporation technique. AES and XRD results show that the new alloy can be regarded as a distorted β-FeSi2 with the Ge participation. The direct band gap of the Ge-Si-Fe alloy was determined to be 0.83eV by optical transmission measurement, which means a red shift of band gap compared with that of β-FeSi2 (Eg=0.87eV).
Gas-Source Molecular Beam Epitaxy of Electronic Devices
Authors: Beam E.A. , Brar B. , Broekaert T.P.E. , Chau H.F. , Liu W. , Seabaugh A.C. 
Published: April 2011

AbstractGas-source molecular beam epitaxy (GSMBE) has been developed into a useful tool for the growth of both optical and electronic device structures. In this paper, we report on the use of tertiarybutylarsine (TBA) and tertiarybutylphosphine (TBP) in GSMBE for the growth of electronic device structures with state-of-the-art performance. Device structures based on both the In0.48Ga0.52P/GaAs and In0.53Ga 0.47As/InP lattice matched materials systems are described. The GSMBE system is based on the use of elemental Group-rn sources and employs thermal crackers for precracking TBA and TBP. Dopant sources include both elemental (Sn and Be) and vapor (CBr4 and SiBr4) sources. Device structures fabricated in the In0.48Ga0.52P/GaAs materials system include single- and double- heterojunction bipolar transistors (SHBTs and DHBTs). Device structures fabricated in the In0.53Ga0.47As/InP materials system include SHBTs, DHBTs, heterojunction field effect transistors (HFETs), and both planar and lateral resonant tunneling diodes (RTDs.) Vertically integrated HFET and multi-RTD heterostructures for high speed logic/memory are also described.
Mbe Growth and Properties of HgCdTe Long Wave and Very Long Wave Infrared Detectors
Authors: Rajavel R. D. , Wu O.K. , Jensen J.E. , Cockrum C.A. , Venzor G.M. , Patten E.A. , Goetz P.M. , Leonard D.B. , Johnson S.M. 
Published: April 2011

Abstractstructural, optical and electrical properties were evaluated. Significant progress has been made toward the growth of high performance HgCdTe devices by molecular beam epitaxy. Long wave infrared detectors operating at 9.9 μm at 78K exhibited a mean RoAoproduct of 1170 Ωcm2at 0-fov. Very long wave infrared detectors operating at 14 μm at 78K exhibited a mean RoA product of 3.5 Ωcm2at f/2 fov. These values represent the state-of-the- art for molecular beam epitaxially grown HgCdTe detectors.
Growth of Epitaxial Gan Films Using Zno Buffer Layer by Pulsed Laser Deposition
Authors: Huang T. F. , Tuncel E. , Yeo J. S. , Harris J. S. 
Published: April 2011

AbstractGaN films and ZnO buffer layers have been deposited on c-cut sapphire substrates by pulsed laser deposition (PLD) employing a KrF laser (λ = 248 nm). The influence of the deposition parameters, such as substrate temperature and gas pressure during growth, have been studied. GaN films grown above 700 °C are single crystalline and the full width of half-maximum (FWHM) of the GaN (0002) peak decreases to 0.37° as the growth temperature increases to 800 °C. The optimum growth pressure for GaN is determined to be 0.01 torr N2. The optical transmission below the bandgap of the GaN film grown at this pressure is over 85%.
Structural Characterization of InAs/(GaIn)Sb Superlattices for IR Optoelectronics
Authors: Wagner J. , Schmitz J. , Fuchs F. , Weimar U. , Herres N. , Tränkle G. , Koidl P. 
Published: April 2011

AbstractWe report on the structural characterization of InAs/(GaIn)Sb superlattices (SL) grown by solid-source molecular-beam epitaxy. SL periodicity and overall structural quality were assessed by high-resolution X-ray diffraction and Raman spectroscopy. Spectroscopic ellipsometry was found to be sensitive to the (GaIn)Sb alloy composition.
Long-Wavelength Vertical-Cavity Surface-Emitting Laser Diodes
Authors: Babic D.I. , Jayaraman V. , Margalit N. M. , Streubel K. , Heimbuch M.E. , Mirin R.P. , Thibeault B.J. , Bowers J.E. , Hu E.L. , Denbaars S. 
Published: April 2011

AbstractLong-wavelength (1300/1550 nm) vertical-cavity surface-emitting lasers (VCSELs) have been much more difficult to realize than VCSELs at shorter wavelengths such as 850/980 nm. The primary reason for this has been the low refractive index difference and reflectivity associated with lattice-matched InP/InGaAsP mirrors. A solution to this problem is to “wafer-fuse” high-reflectivity GaAs/AlGaAs mirrors to InP/InGaAsP active regions. This process has led to the first room-temperature continuous-wave (CW) 1.54 μm VCSELs. In this paper, we discuss two device geometries which employ wafer-fused mirrors, both of which lead to CW operation. We also discuss fabrication of WDM arrays using long-wavelength VCSELs.
Stabilization of Transverse Mode Emission in Vertical-Cavity Surface-Emitting Lasers by Deposition of High Refractive Index Amorphous Gaas
Authors: Park Hyo-Hoon , Yoo Byueng-Su , Chu Hye Yong , Lee El-Hang , Park Min Soo , Ahn Byung Tae , Shin Jae-Heon , Lee Yong Hee 
Published: April 2011

AbstractWe report successful application of a low-temperature-grown amorphous GaAs (a-GaAs) layer for stabilization of the fundamental transverse mode of InGaAs/GaAs vertical-cavity surface-emitting lasers. The maximum currents maintaining a stable fundamental transverse mode were increased by the antiguide effect of a-GaAs with a high refractive index. For 10-μm- and 15-μm-diameter devices, we attained a stable single-mode emission over a wide range of current. The antiguiding of transverse modes in vertical cavity buried in the high refractive cladding layer was calculated using a two-dimensional beam propagation method.
Orientation Dependence Of Surface Passivation For Semi-Insulating Gaas
Authors: Koutzarov I.P. , Edirisinghe C.H. , Ruda H.E. , Jedral L.Z. , Liu Q. , Guo-Ping J. , Xia H. , Lennard W. N. , Rodriguez-Fernandez L. 
Published: April 2011

AbstractWe report on the orientation dependence ((100), (110) and (111) ) of photoluminescence (PL), photoreflectance (PR) and Surface Photo-Voltage (SPV) for sulfur passivated bulk semiinsulating (SI) GaAs. Near band gap PL peak intensities (bound-exciton and acceptor-related) were enhanced following (NH4)2S or S2Cl2 treatment of GaAs for all orientations. The reduction of surface recombination velocity (from PL data) was orientation dependent and especially pronounced for the case of (111)A and (111)B orientations. The effect of thin dielectric layers deposited on S-treated surfaces was also investigated, particularly for (100) and (111)A orientations. SPV data shows a strong increase in the above band gap signal after both Streatment and dielectric film deposition, which was higher than that measured for only S-treated surfaces. PR data showed an increase in the interfacial electric field following deposition of dielectric film. The results of absolute S-surface coverage measurements using particle-induced X-ray emission measurements were correlated with the optical characteristics.
Factors Governing the Photoluminescence Yield of Erbium Implanted Silicon
Authors: Jantsch W. , Przybylinska H. , Skierbiszewski C. , Lanzerstorfer S. , Palmetshofer L. 
Published: April 2011

AbstractWe present a high resolution photoluminescence (PL) study of Si:Er which allows to distinguish a variety of Er centers occurring in Er-implanted Si. The lines belonging to a particular center are identified from the influence of processing parameters, temperature, excitation power, co-doping and hydrostatic pressure. The center-dependent high temperature yield is limited by the competition in efficiency of capturing excitons at Er centers or nearby defects followed by the excitation transfer to the Er-4f shell and by recombination of excitons at other, non-radiative centers. The excitation transfer probability is shown to depend on hydrostatic pressure of a few kbar. This effect indicates a new possibility to improve the efficiency of Si:Er light emitters.
The Effects of Impurity Codoping on the Electrical Properties of Erbium Ions in Crystalline Silicon
Authors: Libertino S. , Coffa S. , Mosca R. , Gombia E. 
Published: April 2011

AbstractWe have investigated the effects of oxygen codoping and thermal annealing on the deep level spectrum and carrier lifetime of Er implanted crystalline Si. It is found that oxygen codoping produces a dramatic modification in the concentration and energetic position of Er-related deep levels in the Si band gap. In particular the formation of Er-O complexes is shown to produce a promotion from deep to shallow levels. This effect is the major responsible of the enhancement of Er donor behaviour in presence of oxygen and also produces a large increase in the minority carrier lifetime
Characterization of Visible and Infrared (1.54 μm) Luminescence from Er-doped Porous Si
Authors: White R. , Wu X. , Hömmerich U. , Namavar F. , Cremins-Costa A. M. 
Published: April 2011

AbstractResults of a photoluminescence excitation (PLE) study of Er-implanted porous Si (Er: PSi) are presented. Erbium was implanted at a dose of 1×1015 Er/cm2 at 380 keV and annealed for 30 minutes at 6507deg;C. We observed a nearly identical PLE intensity behavior from 1.54 μm and visible-emitting Er: PSi. This observation indicates that both visible and infrared photoluminescence (PL) arise from carrier mediated processes, and that the 1.54 μm Er3+ PL is related to the porous Si nanostructures. Measurements of the temperature dependence (15–375K) of Er3+ PL intensity and lifetime are also reported.
Luminescence of Rare Earth Doped Porous Silicon
Authors: Kimura T. , Hosokawa I. , Nishida Y. , Dejima T. , Saito R. , Ikoma T. 
Published: April 2011

AbstractPhotoluminescence characteristics of porous silicon layers (PSLs) doped with Er or Yb ions are studied. 10μm thick PSLs with a luminescence centered at ∼ 0.8μm are formed by anodic etching of p-type silicon wafers of several Ω-cm resistivity. Rare-earth ions are electrochemically incorporated into PSLs. The Er3+-related luminescence at 1.54μm as well as the Yb3+-related luminescence at 1.0μm is observed at room temperature after annealing at high temperatures (>900°C). The Er-related luminescence is enhanced after annealing in O2, whereas the Yb3+-related luminescence needs oxygen-free atmosphere (H2) for the optical activation. The luminescence decay time of the rare earth ions as well as the host PSLs is measured and the energy transfer mechanism is discussed.
Study of the Zeeman Effect of Er3+ in GaAs:Er,O
Authors: Haase Dieter , Dörnen Achim , Takahei Kenichiro , Taguchi Akihito 
Published: April 2011

AbstractWe analyze the Zeeman effect of the 4/13/2 → 4/15/2 transition of Er3+ in GaAs:Er,O grown by metal-organic vapor-phase epitaxy. The photoluminescence spectrum has been assigned previously to one specific Er-O complex. The dominant optical transition at 1538 nm (6499.5 cm−1), which shows a full width at half maximum of only 0.05 cm−1, has been investigated by high-resolution Zeeman spectroscopy. A highly anisotropic Zeeman pattern is found which indicates the low symmetry of the underlying complex. A detailed analysis shows that the defect has a predominant rhombic symmetry C2v,. Additionally, smaller contributions of a crystal field with a monoclinic symmetry Clh are found. The results provide further arguments that an ErO2 complex is the responsible center observed.
Characterization Of Er-Doped III-V Nitride Epilayers Prepared by Mombe
Authors: Zavada J. M. , Wilson R. G. , Schwartz R. N. , MacKenzie J. D. , Abernathy C. R. , Pearton S. J. , Wu X. , Hömmerich U. 
Published: April 2011

AbstractEr-doped AIN epilayers have been grown using metal-organic molecular beam epitaxy (MOMBE) with controlled Er densities. Cell temperatures greater than 1000°C were required for the Er solid source in order to achieve significant Er concentrations in the epilayers. Er densities in the 1019 to 1020 cm−3 range were confirmed using secondary ion mass spectrometry (SIMS), quantified using implanted standards. The epilayers were optically excited using an argon-ion laser and infrared luminescence spectra were measured over the temperature range 13 to 300 K. The spectra are centered at 1.54 μm and display features typical of the Er3+ configuration. These data demonstrate that high densities of Er atoms can be incorporated in AIN films during epitaxial growth and that the Er atoms give rise to the intra-4f transitions of the trivalent Er3+ ion.
Annealing Study of Erbium and Oxygen Implanted Gallium Nitride
Authors: Torvik John T. , Feuerstein Robert J. , Qiu Chang H. , Leksono Moeljanto W , Pankove Jacques I. , Namavar Fereydoon 
Published: April 2011

AbstractA systematic study of photoluminescence (PL) of Er and O ion implanted and annealed n-type GaN grown on R-plane sapphire (A12O3) was performed. The Er implants ranged from 2 × 1013 to 1 × 1015 Er++/cm2, and the O co-implants ranged from 1014 to 1016 O+/cm2. The resulting nine different combinations of GaN:Er,O were annealed at 600 °C (4 hrs. in N2), 700 °C (1.5 hrs. in N2), 800 °C (0.75 hr. in NH3), and 900 °C (0.5 hr. in NH3) Following each annealing step, the Er3 -related PL at 1.54 μm was measured from each sample at 77K, when pumped directly with 135 mW of power at 980 nm. The three samples with the highest dose of Er (1 × 1015 Er++/ cm 2), regardless of O co-dopant dose, yielded the strongest PL peak intensity at 1.54 μm after all the anneals. The integrated PL from 1.52 to 1.58 μm was reduced by 62 % when going from 77 K to room temperature (RT).
Energy-Transfer Processes in Oxygen-Codoped GaAs:Er
Authors: Takahei K. , Hogg R. A. , Taguchi A. 
Published: April 2011

AbstractGaAs grown by metalorganic chemical vapor deposition and codoped with Er and oxygen shows a simple spectrum with sharp luminescence lines due predominantly to one type of Er center. This center is identified as an Er atom substituting a Ga site, coupled with two oxygen atoms. Photoluminescence measurements under host excitation and photoluminescence excitation measurements that directly excite the 4f-shell of the Er3+ ion indicate that this center is excited much more efficiently than other Er centers simultaneously present in the same sample. A possible energy-transfer mechanism and its implications are discussed.