jap banner
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

15 Oct 2002

Volume 92, Issue 8, pp. 4155-4844

Page 2 of 5 Pages Previous Page Next Page | Jump to Page
back to top
RSS Feeds

Optimization of Sm3+ fluorescence in Sm-doped yttrium aluminum garnet: Application to pressure calibration in diamond-anvil cell at high temperature

Carmen Sanchez-Valle, Isabelle Daniel, Bruno Reynard, Robert Abraham, and Christelle Goutaudier

J. Appl. Phys. 92, 4349 (2002); http://dx.doi.org/10.1063/1.1509843 (5 pages) | Cited 9 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Sm3+ concentration in Sm-doped yttrium aluminum garnet (Sm3+:YAG) has been optimized for fluorescence yield and synthesis procedure for the production of strain-free small grain-size powder established. Concentration of 0.5 wt % Sm3+ displays an optimal fluorescence signal, three to five times stronger than the generally proposed concentration (4 wt %). The fluorescence of the samples has been studied as a function of temperature (300–873 K) and pressure (0–15 GPa). A comparison with standard pressure scales shows that the pressure evolution of Sm3+:YAG fluorescence is insensitive to the doping rate, and that temperature has only a limited effect on the pressure scale established at 300 K. The present results indicate that pressure can be determined from the Y1 line of 0.5 wt % Sm-doped YAG, with temperature correction for ϖ at room pressure and constant pressure shift, within the 300–873 K and 10−4−15 GPa pressure-temperature range, through the linear relation: P (GPa)=0.127×[(ϖ0−0.018×ΔT)−ϖ] where ϖ0 corresponds to the Y1 frequency value at ambient conditions (16 185 cm−1). © 2002 American Institute of Physics.
Show PACS
78.55.Hx Other solid inorganic materials
07.35.+k High-pressure apparatus; shock tubes; diamond anvil cells
07.20.Ka High-temperature instrumentation; pyrometers
06.20.F- Units and standards

Investigation of ZnO epilayers grown under various Zn/O ratios by plasma-assisted molecular-beam epitaxy

Hang-Ju Ko, Takafumi Yao, Yefan Chen, and Soon-Ku Hong

J. Appl. Phys. 92, 4354 (2002); http://dx.doi.org/10.1063/1.1509103 (7 pages) | Cited 54 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have investigated ZnO epilayers grown under various Zn/O ratios by plasma-assisted molecular-beam epitaxy. The growth conditions are elucidated by a relationship between growth rate and Zn/O ratios. Surface phase diagrams are obtained by investigation of reflection high-energy electron diffraction. Hexagonal-shaped two-dimensional islands with atomic steps measured by atomic force microscopy are observed on ZnO layers grown under oxygen-rich and stoichiometric flux conditions. On the other hand, ZnO layers grown under Zn-rich conditions exhibit hexagonal pits. The x-ray rocking curve of ZnO samples grown under an oxygen-rich condition is broader than that of ZnO samples grown under stoichiometric or Zn-rich flux conditions, implying a reduction in threading dislocation density. Photoluminescence spectra reveal the strongest intensity from ZnO layers grown under stoichiometric flux conditions, compared with those grown under Zn- and oxygen-rich conditions. The relation between linewidth of the x-ray rocking curve and intensity of photoluminescence suggests that threading dislocations act as nonradiative centers. In conclusion, the Zn/O flux ratio during growth has a strong influence on the quality of ZnO epilayer surfaces, crystal structures, and optical properties. © 2002 American Institute of Physics.
Show PACS
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.-a Thin film structure and morphology
78.55.Et II-VI semiconductors
78.66.Hf II-VI semiconductors
61.66.Bi Elemental solids
61.66.Dk Alloys
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

Photoreflectance spectroscopy of strained (In)GaAsN/GaAs multiple quantum wells

J. B. Héroux, X. Yang, and W. I. Wang

J. Appl. Phys. 92, 4361 (2002); http://dx.doi.org/10.1063/1.1507817 (6 pages) | Cited 32 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effect of a variation of the indium and nitrogen concentrations in InxGa1−xAs1−yNy/GaAs multiquantum wells grown by molecular beam epitaxy is studied systematically by room temperature photoreflectance spectroscopy. The band gap redshift caused by a nitrogen fraction of 1.5% decreases by as much as 30% as the indium fraction increases from 0% to 20%. A moderate increase of electron effective mass (Δme∼0.03 m0) is found in all samples containing nitrogen (y≳1%). In compressively strained quantum wells, the energy separation between the first confined heavy and light hole energy levels decreases in a regular manner as the nitrogen fraction increases from 0% to 1.7%, suggesting that the modification of the valence bands due to nitrogen incorporation can be explained by the strain variation. © 2002 American Institute of Physics.
Show PACS
78.66.Fd III-V semiconductors
73.21.Fg Quantum wells
78.67.De Quantum wells
73.20.Hb Impurity and defect levels; energy states of adsorbed species
78.20.-e Optical properties of bulk materials and thin films

Disorder effects on dielectric response of Si irradiated with Ar+

S. Tripura Sundari

J. Appl. Phys. 92, 4367 (2002); http://dx.doi.org/10.1063/1.1465508 (8 pages) | Cited 4 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Irradiation induced changes in the complex dielectric spectra of single crystal Si are investigated with spectroscopic ellipsometry. The analysis of microstructural variations resulting from ion irradiation is carried out to establish the existence of a well defined amorphization threshold. Increase in fluence leads to amorphization of the crystal resulting in an order–disorder transition as inferred from peak to peak height of the first derivative spectra. The amorphous volume fraction deduced from a microstructure model using effective medium approximation is found to have a power law behavior. The variations in the critical point (CP) structure in the energy range 1.5 to 5 eV is studied as a function of fluence ranging from 6×1013 to 1×1017 Ar+ ions cm−2. The changes in the nature of the CPs is examined in detail by line shape analysis of the second derivative of the optical spectra above and below the amorphization threshold. Irradiation induced structural disorder and its effect on the interband optical transition, particularly the E1 critical point at 3.4 eV is analyzed in detail. The E1 structure is fitted in the complete fluence range with a 2D CP line shape with a large excitonic phase angle. A red shift of the E1 critical point, decrease in its amplitude, increase in excitonic phase angle and broadening of the line shape are observed with increasing fluence. All these parameters of the E1 CP show distinct behavior above and below the amorphization threshold. © 2002 American Institute of Physics.
Show PACS
61.82.Fk Semiconductors
61.80.Jh Ion radiation effects
78.40.Fy Semiconductors
61.72.uf Ge and Si
81.05.Cy Elemental semiconductors
64.70.K- Solid-solid transitions
71.35.Cc Intrinsic properties of excitons; optical absorption spectra

First- and second-order Raman spectra of galena (PbS)

Gregory D. Smith, Steven Firth, Robin J. H. Clark, and Manuel Cardona

J. Appl. Phys. 92, 4375 (2002); http://dx.doi.org/10.1063/1.1505670 (6 pages) | Cited 31 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Raman spectra of cleaved, millimeter-sized single crystals of mineral galena (PbS) have been measured between 100 and 1200 cm−1 over the temperature range 80 to 373 K. Three low wave number bands are observed which can be reconciled with the results of earlier reports. However, changes in the peak wave numbers and in the relative intensities of these bands in response to changes in temperature do not conform with previous assignments for the observed bands. Detailed assignments are proposed which are based on resonance Raman processes. The observed bands are assigned to forbidden longitudinal optical excitations, which are allowed under resonance conditions by a Fröhlich interaction mechanism, and two-phonon excitations. © 2002 American Institute of Physics.
Show PACS
78.30.Hv Other nonmetallic inorganics
63.20.K- Phonon interactions

Morphological and structural analyses of plasma-induced damage to n-type GaN

H. W. Choi, S. J. Chua, and S. Tripathy

J. Appl. Phys. 92, 4381 (2002); http://dx.doi.org/10.1063/1.1509844 (5 pages) | Cited 4 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Plasma-induced damage to n-type GaN has been studied by atomic force microscopy and Raman spectroscopy. It was found that the extent of surface roughening is largely dependent on the surface defect density, since preferential sputtering at these sites takes place. Several Raman defect modes have emerged from the plasma-damaged samples, and have been compared to the defect modes observed from ion-implanted GaN. The defect peaks centered at 300 and 360 cm−1 have been assigned to disorder-activated Raman scattering modes, while the 453 and 639 cm−1 peaks have been attributed to vacancy scattering. It has also been demonstrated that structural damage can be annealed out at 900 °C for 60 s in flowing N2. © 2002 American Institute of Physics.
Show PACS
81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
81.05.Ea III-V semiconductors
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.Cc Kinetics of defect formation and annealing
68.37.Ps Atomic force microscopy (AFM)
78.30.Hv Other nonmetallic inorganics
78.68.+m Optical properties of surfaces

Optical constants and roughness study of dc magnetron sputtered iridium films

Li Yan and John A. Woollam

J. Appl. Phys. 92, 4386 (2002); http://dx.doi.org/10.1063/1.1509091 (7 pages) | Cited 4 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Extremely smooth thin films of iridium have been deposited onto superpolished fused silica substrates using dc magnetron sputtering in an argon plasma. The influence of deposition process parameters on film microroughness has been investigated. In addition, film optical constants have been determined using variable angle spectroscopic ellipsometry, over the spectral range from vacuum ultraviolet to middle infrared (140 nm–35 μm). Because the Ir films were optically thick and the surface roughnesses were measured by atomic force microscopy then accounted for in the optical model, the as-determined film optical constants are expected to be the best available for Ir bulk metals, minimally affected by surface overlayers or microstructure. © 2002 American Institute of Physics.
Show PACS
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.66.Bz Metals and metallic alloys
68.55.-a Thin film structure and morphology
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ps Atomic force microscopy (AFM)
back to top
RSS Feeds

Microstructure and thermoelectric properties of Cr-doped β-FeSi2 sintered with micrograins treated in radio frequency plasmas of SiH4 and GeH4 gases

Kengo Kishimoto, Yasuyuki Nagamoto, Toshikatsu Miki, Tsuyoshi Koyanagi, and Kakuei Matsubara

J. Appl. Phys. 92, 4393 (2002); http://dx.doi.org/10.1063/1.1507814 (9 pages)

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Microstructural control by means of plasma treatment was performed on sintered Cr-doped β-FeSi2 in order to improve its thermoelectric properties. The micrograins were exposed to rf plasmas of germane (GeH4) or a mixture of germane and silane (SiH4) and were then sintered. The thermoelectric properties of the samples were investigated along with their microstructures. The results show that the plasma treatments reduced thermal conductivity and increased electrical conductivity and mobility, which led to an increase in thermoelectric figure-of-merit. In addition, the results show that the plasma treatments also formed small SiGe crystals distributed throughout the samples, removed most of the grain boundaries, and sometimes formed FeSi crystals. The relation between the changes in the thermoelectric properties and the modification of the microstructure was discussed. It was found that the microstructural modification by the plasma treatment caused favorable changes in thermoelectric properties. © 2002 American Institute of Physics.
Show PACS
72.20.Pa Thermoelectric and thermomagnetic effects
61.72.Mm Grain and twin boundaries
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
72.80.Jc Other crystalline inorganic semiconductors
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
52.77.-j Plasma applications

Electrical resistivity of steels and face-centered-cubic iron

Ulrich Bohnenkamp, Rolf Sandström, and Göran Grimvall

J. Appl. Phys. 92, 4402 (2002); http://dx.doi.org/10.1063/1.1502182 (6 pages) | Cited 5 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Literature data for the electrical resistivity of austenitic and ferritic steels are analyzed in a model that takes into account their composition and microstructure. The resistivity in these systems is so high that one must allow for its saturation. That effect is described with the shunt-resistor model, and saturation at 1.68 μΩm. Our analysis yields the contributions to the resistivity of austenite per weight percent from the solute elements N, C, Nb, Si, Ti, Cu, Ni, Cr, and Mo, with the contribution decreasing in this order. For ferrite, the contribution of the solute elements Si, Mn, Cu, Ni, Mo, and Cr was determined, with the contribution decreasing in this order. The data allow us to obtain the previously unknown resistivity of metastable pure γ-iron (fcc Fe) near room temperature, and find an interpolation formula for the resistivity up to 1183 K where the γ phase becomes stable. The resistivity in metastable γ-iron is significantly larger than the resistivity in stable α-Fe (bcc Fe) below 1000 K. This difference is attributed to a strong electron scattering due to spin disorder in γ-iron at intermediate temperatures. © 2002 American Institute of Physics.
Show PACS
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
81.30.Bx Phase diagrams of metals, alloys, and oxides

Effects of charge transfer on a-SiO2 surface structure: A molecular dynamics study

Cheng Wang, Nobu Kuzuu, and Yoshimori Tamai

J. Appl. Phys. 92, 4408 (2002); http://dx.doi.org/10.1063/1.1506392 (6 pages) | Cited 1 time

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effects of charge transfer between atoms on an amorphous SiO2 surface were studied by comparing a model with fixed charge (FQ) and a model that takes into consideration charge transfer by the charge equilibration (QEq) method. The QEq surface has more oxygen atoms and denser structures compared to the FQ sample. We found, on the surface of the QEq sample, three-coordinated Si with an O–Si–O bond angle in the range of 109–115°. This structure is similar to that of the experimentally observed E′ center (≡Si⋅). We also found a structure similar to the nonbridging oxygen hole center (≡Si–O⋅), which has been observed experimentally on a silica glass surface. These structures were not observed in the FQ model. The results suggest that consideration of the charge transfer is essential to reproduce the defect structure of the silica glass surface. © 2002 American Institute of Physics.
Show PACS
61.43.Bn Structural modeling: serial-addition models, computer simulation
68.35.B- Structure of clean surfaces (and surface reconstruction)
61.43.Fs Glasses

Random telegraph signal noise in SiGe heterojunction bipolar transistors

Martin von Haartman, Martin Sandén, Mikael Östling, and Gijs Bosman

J. Appl. Phys. 92, 4414 (2002); http://dx.doi.org/10.1063/1.1506197 (8 pages) | Cited 5 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this work, random telegraph signal (RTS) noise in SiGe heterojunction bipolar transistors (HBTs) was characterized both as a function of bias voltage and temperature. The RTS amplitudes were found to scale with the total base current, and the characteristic times in the higher and lower RTS state were found to decrease rapidly with bias voltage, approximately as 1/exp(qVBE/kT) or stronger. The RTS amplitudes were explained by a model based on voltage barrier height fluctuations across the base–emitter junction induced by trapped carriers in the space charge region. It was shown that the relative RTS amplitudes ΔIB/IB decrease exponentially with temperature in this model, which also was verified by measurements. The trapping/detrapping mechanism was suggested to be electron and hole capture, where the hole capture process occurs by tunneling. The characteristic times in both the lower and higher RTS state were in some cases found to decrease exponentially with temperature, characteristic for a thermally activated process, and in some cases found to be only weakly temperature dependent. The former behavior was explained by a multiphonon process with thermally activated capture cross sections, and an activation energy of 0.39 eV was extracted. RTS amplitudes proportional to the nonideal base current component or weaker were also found, originating from traps at the Si/SiO2 interface at the emitter periphery. The trapped carriers affect the recombination rate in the base–emitter space charge region, probably by changing the number of carriers. In this case, ΔIB/IB only showed a weak temperature dependence, which correlates well with this model. Characteristic times that decreased exponentially with temperature were observed, originating from a multiphonon process in the SiO2 with an activation energy for the capture cross section of 0.29 eV. © 2002 American Institute of Physics.
Show PACS
85.30.Pq Bipolar transistors

Band structures of Ge and InAs: A 20 k.p model

S. Ben Radhia, S. Ridene, K. Boujdaria, H. Bouchriha, and G. Fishman

J. Appl. Phys. 92, 4422 (2002); http://dx.doi.org/10.1063/1.1505990 (9 pages) | Cited 13 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The band structure of direct-band-gap semiconductor (InAs) and indirect-band-gap semiconductor (Ge) is described theoretically using a 20×20 k.p model and including far-level contribution (essentially the d levels). By using this model, we obtained a quantitatively correct description of the top of the valence band and the lowest two conduction bands both in terms of energetic positions and band curvatures. In particular, the k.p Hamiltonian parameters are adjusted such that the transverse mass of the germanium conduction band is equal to the experimental value of 0.081. © 2002 American Institute of Physics.
Show PACS
71.20.Mq Elemental semiconductors
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
71.20.Nr Semiconductor compounds
71.15.-m Methods of electronic structure calculations

Electronic susceptibility in thin films and interfaces

John R. Jameson, Walter Harrison, and P. B. Griffin

J. Appl. Phys. 92, 4431 (2002); http://dx.doi.org/10.1063/1.1507812 (10 pages) | Cited 5 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We use tight-binding theory to investigate the electronic contribution to dielectric susceptibility in thin films and interfaces of covalent materials. We begin by describing the effects of an electric field on the elemental unit of a covalent material, the bond. Then, we show how the responses of individual bonds can be added up to obtain an estimate of the susceptibility of a bulk material. In doing so, we see that the polarization of a material can be viewed as arising from the transfer of charge from one side of the system to the other, and that this viewpoint leads naturally to a local definition of susceptibility in semiconductors. Using this concept, we examine dielectric susceptibility in thin films and interfaces, with a Si/Ge/Si heterostructure serving as an example. The interesting feature of thin films and interfaces is that they exhibit spatial variations in susceptibility, which we attribute to: (i) elastic distortions; (ii) the creation of bonds at an interface which are of a type not found in either bulk material; and (iii) the coupling of a bond to neighboring antibonds different than those in the bulk material. We then ask what error is introduced by neglecting these local variations when calculating the capacitance of a multilayer dielectric. For the Si/Ge/Si heterostructure, we find that effect (iii) introduces only small errors, even for very thin Ge layers, because the decrease in susceptibility on the Ge side of an interface is offset by the increase in susceptibility on the Si side. Similarly, effect (ii) is small because the polarizability of the Si–Ge bonds at the interface is very nearly the average of that for Si and Ge. On the other hand, effect (i) does lead to noticeable errors, but these errors can be removed almost entirely by choosing the permittivity of the Ge layer to be that of bulk Ge under the same state of strain as the Ge layer in the heterostructure. We conclude by interpreting recent experiments on “high-k” dielectrics in term of what we have learned here. [C. M. Perkins et al., Appl. Phys. Lett. 78, 2357 (2001); M. Koyama et al., Tech. Dig. Int. Electron Devices Meet., 459 (2001); W.-J. Qi et al., ibid., 145 (1999)]. © 2002 American Institute of Physics.
Show PACS
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Cw Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
68.35.Np Adhesion
73.20.At Surface states, band structure, electron density of states
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)

Impact of localized states on the recombination dynamics in InGaN/GaN quantum well structures

Shih-Wei Feng, Yung-Chen Cheng, Yi-Yin Chung, C. C. Yang, Yen-Sheng Lin, Chen Hsu, Kung-Jeng Ma, and Jen-Inn Chyi

J. Appl. Phys. 92, 4441 (2002); http://dx.doi.org/10.1063/1.1506393 (8 pages) | Cited 27 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Multiple-component decays of photoluminescence (PL) in InGaN/GaN quantum wells have been widely reported. However, their physical interpretations have not been well discussed yet. Based on wavelength-dependent and temperature-varying time-resolved PL measurements, the mechanism of carrier transport among different levels of localized states (spatially distributed) in such an indium aggregated structure was proposed for interpreting the early-stage fast decay, delayed slow rise, and extended slow decay of PL intensity. Three samples of the same quantum well geometry but different nominal indium contents, and hence different degrees of indium aggregation and carrier localization, were compared. The process of carrier transport was enhanced with a certain amount of thermal energy for overcoming potential barriers between spatially distributed potential minimums. In samples of higher indium contents, more complicated carrier localization potential structures led to enhanced carrier transport activities. Free exciton behaviors of the three samples at high temperatures are consistent with previously reported transmission electron microscopy results. © 2002 American Institute of Physics.
Show PACS
73.63.Hs Quantum wells
78.67.De Quantum wells
73.21.Fg Quantum wells
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
72.80.Ey III-V and II-VI semiconductors
78.55.Cr III-V semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.35.-y Excitons and related phenomena

Characterization of ultrathin metal–oxide–semiconductor structures using coupled current and capacitance–voltage models based on quantum calculation

O. Simonetti, T. Maurel, and M. Jourdain

J. Appl. Phys. 92, 4449 (2002); http://dx.doi.org/10.1063/1.1506000 (10 pages) | Cited 9 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We have developed a capacitance–voltage (C–V) and a current–voltage (I–V) quasistatic quantum model of ultrathin metal–oxide–semiconductor (MOS) structures based on the self-consistent solution of the Schrödinger and Poisson equations. The direct tunneling current takes into account the carrier distribution in energy subbands and uses the notions of corrected tunnel transparency and of impact frequency at the injecting electrode. These models are used to obtain the main physical parameters of n+-polysilicon/SiO2/〈100〉 p-Si MOS structures, with oxide thickness ranging from 1.2 to 3.5 nm. The extracted parameters are the oxide thickness (TOX), the substrate doping, both at the Si/SiO2 interface [NS(0)] and deep in the bulk [NS(∞)], and the polysilicon gate doping (NP) near the polysilicon/SiO2 interface. For this range of oxide thickness, the direct tunneling current strongly perturbs the C–V measurements, which must be corrected. Down to 1.5 nm oxide thickness, these parameters are obtained by C–V characterization. Below 1.5 nm oxide thickness, the C–V correction fails and TOX is obtained by a coupled C–V and I–V characterization procedure, based on the adjustment of the effective mass of the electrons in the oxide (mOX) with the oxide thickness. The whole characterization procedure provides TOX values with associated errors very close to the ellipsometric measurements. The information obtained on the substrate doping seems to correspond well with advanced MOS technologies. The C–V and I–V simulation results are in good agreement with measurements for all the samples and a good consistency is found between the C–V and I–V models. Finally, we show that the extracted TOX obtained with the variation of mOX with TOX provide a better agreement than those with a constant mOX value, compared to the ellipsometric measurements. © 2002 American Institute of Physics.
Show PACS
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
03.65.Sq Semiclassical theories and applications
73.20.At Surface states, band structure, electron density of states
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
03.65.Ge Solutions of wave equations: bound states

Performance analysis of lateral p–n junction laser-transistor

V. Ryzhii, A. Satou, I. Khmyrova, T. Ikegami, K. Kubota, P. O. Vaccaro, J. M. Zanardi Ocampo, and T. Aida

J. Appl. Phys. 92, 4459 (2002); http://dx.doi.org/10.1063/1.1507813 (6 pages) | Cited 3 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We study the performance of a lateral p–n junction quantum-well edge-emitting laser-transistor with an extra gate contact. The incorporation of the gate contact provides an opportunity to control the threshold current and output optical power by the gate voltage. The application of negative gate voltages can lead to a substantial decrease in the threshold current. This is due to the confinement of the electrons injected into the p-type portion of the quantum well serving as the active region. Using the developed device model, we calculate the laser-transistor threshold and output characteristics. We also estimate the device cutoff modulation frequency associated with the gate recharging. © 2002 American Institute of Physics.
Show PACS
42.55.Px Semiconductor lasers; laser diodes
42.60.By Design of specific laser systems

Capacitance dispersion in ion implanted 4H and 6H-silicon carbide

A. O. Evwaraye, S. R. Smith, W. C. Mitchel, and M. A. Capano

J. Appl. Phys. 92, 4465 (2002); http://dx.doi.org/10.1063/1.1505692 (5 pages)

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Nitrogen doped 4H–SiC and 6H–SiC epitaxial layers with net doping concentration of 1.5×1015 cm−3 were implanted with either Al, B, or Ar ions at 600 °C. The energy of the ions was 160 keV and at a dose of 2×1016 cm−2. After annealing at 1600 °C for 5–60 min, Schottky diodes were fabricated on the samples. The measured junction capacitance of ion implanted samples varies with both temperature and frequency. The thermal activation energy determined from the frequency break ωB ranges from 183 to 202 meV. The Ar implanted samples remain n-type and show no capacitive dispersion. Similarly, the junction capacitance of samples doped with Al does not exhibit dispersion. It is suggested that the implantation induced defects play a role in the observed dispersion. The data show that the series resistance is insignificant and does not account for the observed dispersion. © 2002 American Institute of Physics.
Show PACS
61.72.up Other materials
85.30.Kk Junction diodes
61.72.Cc Kinetics of defect formation and annealing

Study of the electronic structure of amorphous and crystallized low pressure chemically vapor deposited silicon films near the absorption threshold

D. Davazoglou and D. N. Kouvatsos

J. Appl. Phys. 92, 4470 (2002); http://dx.doi.org/10.1063/1.1508431 (5 pages) | Cited 2 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Silicon films were chemically vapor deposited on quartz substrates from SiH4 decomposition in a conventional reactor at 230 mTorr and at a temperature of 550 °C. Samples were subsequently doped with phosphorus at a concentration of 1018 cm−3 and oxidized, in order to increase the grain size and to enhance crystallization. The optical properties of these films were studied with optical transmission measurements below their absorption threshold taken after every processing step, which were analyzed with the aid of a two-band model proposed by R. Forouhi and I. Bloomer [Phys. Rev. B 34, 7018 (1986)]. It was found that the energetic distance, separation, and magnitude of the Forouhi–Bloomer (FB) bands change with the various post-deposition treatments. For the as-deposited (amorphous) films, the FB model provides a picture of the distribution of the density of states (DOS) in very good agreement with that of vacuum evaporated films measured in the past with photoelectron spectroscopy. X-ray diffraction measurements taken on crystallized samples have shown that grains were oriented with the (111) and (220) crystallographic axes normal to the substrate. It was shown that the orientation of grains affects significantly the DOS and hence the optical properties of films, which are in this case influenced by electronic transitions near the L and K points of the Brillouin zone of Si [corresponding to the (111) and (220) crystallographic directions]. © 2002 American Institute of Physics.
Show PACS
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
73.61.Cw Elemental semiconductors
78.66.Db Elemental semiconductors and insulators
68.55.-a Thin film structure and morphology

Multidimensional, closed-form analytic expressions for mobilities in Ga1−xAlxAs heterostructures

Herbert S. Bennett

J. Appl. Phys. 92, 4475 (2002); http://dx.doi.org/10.1063/1.1507815 (11 pages) | Cited 1 time

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A significant, practical challenge, which arises in developing computationally efficient physical models for use in computer simulations of microelectronic and optoelectronic devices (for example, transistors in digital cellular phones and in laser modulators, respectively), is to represent vast amounts of numerical data for transport properties in two or more dimensions in terms of closed- form analytic expressions. In this article, we use a methodology, which was presented in more detail previously, to achieve the above goal for a class of numerical data in a bounded two-dimensional space. We present here closed-form analytic expressions for the electron and hole mobilities at 300 K in p-type and n-type Ga1−xAlxAs as functions of dopant densities between 1016 and 1020 cm−3 and mole fractions of AlAs with x between 0.0 and 0.3. This methodology and its associated principles, strategies, regression analyses, and graphics are expected to be applicable to other problems beyond the specific case of mobilities addressed in this article. © 2002 American Institute of Physics.
Show PACS
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.61.Ey III-V semiconductors
73.50.Dn Low-field transport and mobility; piezoresistance

Transport in random quantum dot superlattices

I. Gómez, F. Domínguez-Adame, E. Diez, and P. Orellana

J. Appl. Phys. 92, 4486 (2002); http://dx.doi.org/10.1063/1.1503393 (4 pages) | Cited 8 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present a model based on the two-dimensional transfer matrix formalism to calculate single-electron states in a random wide-gap semiconductor quantum dot superlattice. With a simple disorder model both the random arrangement of quantum dots (configurational disorder) and the spatial inhomogeneities of their shape (morphological disorder) are considered. The model correctly describes channel mixing and broadening of allowed energy bands due to elastic electron scattering by disorder. © 2002 American Institute of Physics.
Show PACS
73.63.Kv Quantum dots
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Hot-electron-temperature relaxation time in a two-dimensional electron gas: AlGaN/GaN at 80 K

A. Matulionis, R. Katilius, J. Liberis, L. Ardaravičius, L. F. Eastman, J. R. Shealy, and J. Smart

J. Appl. Phys. 92, 4490 (2002); http://dx.doi.org/10.1063/1.1510166 (8 pages) | Cited 14 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The electron temperature method is developed for a high-density two-dimensional electron gas (2DEG). The relation of electronic noise and transport properties is obtained in the case of weakly inelastic scattering without considering the scattering mechanisms in detail. The method is applied to consider the experimental data on AlGaN/GaN 2DEG channels. The electron-temperature relaxation time and its dependence on electric field are extracted from the current–voltage and noise–voltage characteristics measured for two-terminal samples at 80 K. The method works in the field range up to 3 kV/cm in the considered 2DEG channels. In this range of fields, the electron temperature reaches 350 K, and the electron–temperature relaxation time diminishes from 5 ps at low fields to 0.4 ps at 3 kV/cm. © 2002 American Institute of Physics.
Show PACS
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Td Noise processes and phenomena
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.20.At Surface states, band structure, electron density of states
73.61.Ey III-V semiconductors

Mechanism of carrier transport in aluminum-doped zinc oxide

Radhouane Bel Hadj Tahar and Noureddine Bel Hadj Tahar

J. Appl. Phys. 92, 4498 (2002); http://dx.doi.org/10.1063/1.1509083 (4 pages) | Cited 22 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The conduction mechanism in aluminum-doped zinc oxide has been studied. Structural investigation shows that crystallographic orientation as well as grain boundary scattering can be neglected. Based on the analysis of the Hall mobility, it has been found that scattering at neutral and ionized impurities dominates the mobility. Further improvement in the mobility can be achieved by lowering the density of neutral impurities through careful control of the film processing parameters. © 2002 American Institute of Physics.
Show PACS
73.61.Ga II-VI semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
61.72.Mm Grain and twin boundaries
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths

Low-frequency noise and current–voltage characteristics of Schottky barrier contacts in a wide temperature range

V. G. Bozhkov and D. Ju. Kuzyakov

J. Appl. Phys. 92, 4502 (2002); http://dx.doi.org/10.1063/1.1502918 (11 pages) | Cited 10 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The low-frequency (1/f) noise and current–voltage characteristics of GaAs and Si Schottky barrier diodes are studied over a wide temperature range: 77–400 K. The peculiarities of temperature and current dependences of the spectral intensity (SI) of current fluctuations Si(I,T) (a specific increase of the SI with decrease in temperature and a deviation from a quadratic dependence of the Si–I2 form) are explained adequately by the influence of a predominantly local barrier height lowering at a Schottky barrier contact (SBC), most likely at its periphery. The Gaussian barrier height distribution at SBCs does not explain these peculiarities. It is shown that the 1/f noise at SBCs approaches the “ideal” noise of the Si–Iβ/fα form, where β=2 and α=1, as the temperature increases. The explanation for the “low-temperature anomaly” in SBCs [an increase in the ideality factor n and a decrease in the measured (from a saturation current) barrier height φbm with decrease in temperature, a weak variation of their product φbn≡nφbm in this case, and the character of the temperature dependence n(T) in the form of n≅1+T0/T (“T0 effect”)] is presented. This explanation is based on a fundamental property of real SBCs—the nonlinear bias dependence of the barrier height resulting in a growth of the ideality factor with a bias voltage (current) increase. The other necessary condition for revealing the “low-temperature anomaly” is the inclusion in theory of the fact that the n and φbm measurements are performed at the same current for all temperatures. An expression for the flatband barrier height φbf is derived. It takes into account the nonlinear bias dependence of the barrier height and the n(I) dependence which follows from it. On the basis of this expression the conditions are defined at which a simple approximation for φbf is valid: φbf≅φbn≡nφbm. © 2002 American Institute of Physics.
Show PACS
73.30.+y Surface double layers, Schottky barriers, and work functions
72.70.+m Noise processes and phenomena
85.30.Kk Junction diodes
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Background charge fluctuations and the transport properties of biopolymer-gold nanoparticle complexes

C. A. Berven, M. N. Wybourne, L. Clarke, L. Longstreth, J. E. Hutchison, and J. L. Mooster

J. Appl. Phys. 92, 4513 (2002); http://dx.doi.org/10.1063/1.1506399 (5 pages) | Cited 12 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The room temperature electrical characteristics of biopolymer-gold nanoparticle complexes show threshold behavior, periodic conductance features, and current–voltage scaling that together indicate the nonlinear transport is associated with single electron charging. Repeated measurements over a period of up to 80 h showed the characteristics change with time. The current–voltage scaling behavior is found to be time independent, while the position of the conductance features shifted randomly over periods of many hours. We show that the time dependence is consistent with a fluctuating background charge distribution and can be understood within the framework of the orthodox model of single electron transport that is modified to account for the relatively large self-capacitance of the nanoparticles. © 2002 American Institute of Physics.
Show PACS
72.15.Nj Collective modes (e.g., in one-dimensional conductors)
72.80.Tm Composite materials
back to top
RSS Feeds

Structural, magnetic, and transport studies of La0.8MnO3 films

Q. Qian, T. A. Tyson, C. Dubourdieu, A. Bossak, J. P. Sénateur, M. Deleon, J. Bai, G. Bonfait, and J. Maria

J. Appl. Phys. 92, 4518 (2002); http://dx.doi.org/10.1063/1.1505667 (6 pages) | Cited 3 times

Online Publication Date: 1 October 2002

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A study of the properties of La0.8MnO3 films of varying thickness was performed. Transport and magnetization measurements show that the ferromagnetic (metallic) volume fraction of the film varies from ∼ 1/4 for ultrathin 60  Å films to ∼ 1/2 for 1600  Å films. Multilength scale structural measurements reveal that near 300  Å, a transition from highly strained ultrathin films to relaxed bulk-like films occurs. The transition region is characterized by low surface roughness, high crystallite orientation, and broad d-spacing distributions. © 2002 American Institute of Physics.
Show PACS
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Dd Nonmetallic ferromagnetic materials
73.61.Ng Insulators
68.55.-a Thin film structure and morphology
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
Page 2 of 5 Pages Previous Page Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close