bluuebunny/crossref_metadata_2025 huggingface dataset:
Long wavelength GaSb photoconductive detectors grown on Si substrates
Authors: Levine B. F. , Malik R. J. , Bethea C. G. , Walker J.
Published: July 2002

We report the first long wavelength photoconductive detectors fabricated from GaSb epitaxially grown on Si substrates. Responsivities of 0.18 A/W are obtained at a wavelength of 1.5 μm.
Observation of kinetically controlled monolayer step height distribution at normal and inverted interfaces in ultrathin GaAs/AlxGa1−xAs quantum wells
Authors: Voillot F. , Madhukar A. , Kim J. Y. , Chen P. , Cho N. M. , Tang W. C. , Newman P. G.
Published: July 2002

We report on comparative photoluminescence (PL) studies of GaAs/Al0.33Ga0.67As single quantum well structures grown via molecular beam epitaxy under identical growth conditions employing (a) customary practice of no growth interruption and (b) growth interruption. The growth conditions themselves are chosen to be near optimum, as determined from the growth kinetics exemplified by the reflection high-energy electron diffraction intensity dynamics. Results show PL lines with fine structure and widths among the narrowest ever reported for 28.3 and 56.6 Å wells. The fine structure is indicative of kinetically controlled interfaces with a predominant step height of one atomic layer and the linewidths a first measurement of intrinsic alloy disorder scattering.
Polarization switching in a strip grating coupled optically pumped submillimeter laser
Authors: Whitbourn L. B. , Macfarlane J. C. , Falconer I. S. , James B. W. , Stimson P. A.
Published: July 2002

It is shown that an optically pumped formic acid laser operating at 394 or 433 μm can lase on two sets of nondegenerate orthogonally polarized modes when a strip grating output coupler is used. The laser output polarization can be switched from parallel to perpendicular to the strips by a small cavity length change which is in accordance with calculated reflection phase changes of the grating for the two polarizations. For 30 W pump power ∼5 mW can be obtained at 394 μm in either polarization when the grating strips are oriented perpendicular to the pump polarization.
Anomalous temperature dependence of lattice parameters of metalorganic chemical vapor deposition CdTe grown on GaAs
Authors: Staudenmann J.-L. , Horning R. D. , Knox R. D. , Arch D. K. , Schmit J. L.
Published: July 2002

It is reported that the lattice parameters of a 3-μm-thick [1,0,0] single crystal CdTe epitaxial layer on a [1,0,0] single crystal GaAs substrate behave anomalously below 120 K. The epilayer used in this experiment was deposited at 410 °C by metalorganic chemical vapor deposition. This x-ray lattice parameter study was done in the temperature range between about 8 and 300 K. Our results show that the lattice parameters perpendicular to the surface of both the GaAs substrate and the CdTe epilayer shrink four times more than the corresponding bulks when the samples are cooled down to 10 K. It is further seen that there is no compensation effect between the elements of the composite system; that is, the lattice parameters of the two materials change in the same direction as if the composite system—the epilayer and the thickness of the substrate which is probed by the x rays—would behave as a new material with entirely new physical properties.
Narrow-stripe metal-clad ridge-waveguide laser for 1.3 μm wavelength
Authors: Amann Markus-Christian , Stegmüller Bernhard
Published: July 2002

Metal-clad ridge-waveguide lasers with stripe widths between 1.5 and 3 μm have been developed in InGaAsP-InP for 1.3 μm wavelength. By an appropriate design for these lasers, threshold currents as low as 20 mA are achieved for 200-μm-long cavities. The corresponding low heat dissipation enables cw operation of upside-down mounted devices up to 85 °C heat sink temperature.
High efficiency polycrystalline silicon solar cells using phosphorus pretreatment
Authors: Narayanan S. , Wenham S. R. , Green M. A.
Published: July 2002

Recent improvements in crystalline silicon solar cell energy conversion efficiency to beyond 20% have been obtained by combining surface oxide passivation with high quality, low resistivity substrates. The objective of the present work was to evaluate the effectiveness of these techniques in improving efficiency on lower quality cast polycrystalline silicon. Due to the poorer crystallographic quality and higher levels of secondary impurities, an additional phosphorus pretreatment was found to reliably improve the performance of the polycrystalline cells above those fabricated without this pretreatment. Cell energy conversion efficiencies were notably higher than previously reported for the present material with values in the 15.3–16.0% range obtained for p-type substrates of 0.1–1 Ω cm resistivity.
Infrared spectrophotometry of carbon-induced localized vibrational mode in indium-doped liquid-encapsulated Czochralski GaAs
Authors: Kitagawara Y. , Itoh T. , Noto N. , Takenaka T.
Published: July 2002

Infrared absorption measurements are performed for a carbon-induced localized vibrational mode in indium-doped semi-insulating GaAs crystals. Increase of the indium concentration in GaAs is found to result in a shift of the absorption peak to the lower energy side and a broadening of full width at half-maximum of the peak. The peak shift of 1 cm−1 corresponds to the change of indium concentration by 2.7×1020 cm−3. For a quantitative analysis of carbon, infrared absorptions are compared with carbon concentrations measured by secondary ion mass spectrometry. The absorption intensity of 1 cm−2 is found to correspond to the carbon concentration of (2.3±1.0)×1016 cm−3.
Hg content of anodic oxide films on Hg1−xCdxTe after heat treatment as measured by 40 MeV-O5+ ion backscattering
Authors: Takita K. , Ippōshi T. , Murakami K. , Masuda K. , Kudo H. , Seki S.
Published: July 2002

The Hg concentration of anodic oxide films on Hg1−xCdxTe and its change after heat treatment were investigated by using 40 MeV-O5+ backscattering. Heat treatment in a vacuum for 60 min was performed at various temperatures up to 350 and 400 °C, respectively, for the samples with x=0.19 and x=0.32. A significant Hg content in the as-grown anodic oxide was found in accordance with the recent result of C. M. Stahle, D. J. Thomson, C. R. Helms, C. H. Becker, and A. Simmons [Appl. Phys. Lett. 47, 521 (1985)]. The Hg in the film gradually decreased with increasing heat treatment temperature up to about 290 °C and rapidly disappeared above 290 °C for both x=0.19 and x=0.32.
Subpicosecond excitonic electroabsorption in room-temperature quantum wells
Authors: Knox W. H. , Miller D. A. B. , Damen T. C. , Chemla D. S. , Shank C. V. , Gossard A. C.
Published: July 2002

We investigate the dynamics of excitonic optical absorption in room-temperature GaAs quantum wells during the application of a rapidly changing electric field in the plane of the quantum well layers. We obtain electroabsorptive modulation with a response time constant of 330 fs, which is the fastest ever reported in a semiconductor.
Dopant redistribution in silicon-on-sapphire films during thermal annealing
Authors: Cowern N. E. B. , Yallup K. J. , Godfrey D. J.
Published: July 2002

Arsenic depth distributions in silicon-on-sapphire films, after annealing at 900 °C for a range of times, have been studied by Rutherford backscattering and spreading resistance techniques. A continuum pipe diffusion model is developed which accounts satisfactorily for the rapid diffusion and segregation effects observed. In addition, the same model predicts two-dimensional dopant profiles with several novel features relevant to microelectronic device processing.
Homogeneity qualification of GaAs substrates for large scale integration applications
Authors: Maluenda J. , Martin G. M. , Schink H. , Packeiser G.
Published: July 2002

A novel procedure is used to qualify the homogeneity of GaAs substrates for large scale integration (LSI) circuit applications. This procedure is particularly well adapted for assessing the electrical variations of densely packed field-effect transistors (FET’s) used in GaAs LSI circuits. Threshold voltage nonuniformity due to crystal inhomogeneity and surface effects is measured for both conventional and In-alloyed, dislocation-free, slightly Cr-doped, semi-insulating liquid encapsulated Czochralski substrates. The average value of the threshold voltage standard deviation of about 300 dense rows over a 2-in.-diam wafer (30 FET’s over 300 μm for each row) is 20 mV using dislocation-free substrates which is much smaller than in conventional substrates (50–100 mV). These data show the importance of this qualification test with the highest ever reported resolution of 10 μm suitable for the evaluation of fabrication yield of LSI circuits.
Continuous wave operation of ridge waveguide AlGaAs/GaAs distributed feedback lasers with low threshold current
Authors: Noda Susumu , Kojima Keisuke , Mitsunaga Kazumasa , Kyuma Kazuo , Nakayama Takashi
Published: July 2002

Ridge waveguide AlGaAs/GaAs distributed feedback lasers were fabricated by a two-step molecular beam epitaxial growth technique. A threshold current as low as 42 mA, which is the lowest ever reported, was obtained under a continuous wave condition at room temperature. Stable single longitudinal mode oscillation was observed in the temperature range from −20 to 30 °C without any suppression of the Fabry–Perot mode.
Vapor diffused optical waveguides in strontium barium niobate (SBN: 60)
Authors: Eknoyan O. , Bulmer C. H. , Taylor H. F. , Burns W. K. , Greenblatt A. S. , Beach L. A. , Neurgaonkar R. R.
Published: July 2002

Single mode planar and channel waveguides have been produced in Sr0.6Ba0.4Nb2O6 (tungsten bronze structure) by sulfur diffusion in a sealed ampule, followed by oxidation in an open tube. Losses in channel waveguides were ∼15–20 dB/cm for TM polarization and ∼27–32 dB/cm for the TE polarization in z-cut substrates. Electro-optic modulation was observed after poling of the substrate. The experimentally determined value of the effective electro-optic coefficient was slightly greater than reported earlier for bulk samples of SBN:60, and about 15 times greater than for LiNbO3. Based on measurements with the S35 radioisotope, the average atomic sulfur concentration was estimated to be about 4×1017/cm3 in the region extending from the surface to a depth of 2.5 μm, and a significant background concentration (∼5×1016/cm3) was present to depths in excess of 20 μm.
InGaAs/InAlAs hot-electron transistor
Authors: Reddy U. K. , Chen J. , Peng C. K. , Morkoç H.
Published: July 2002

Using InGaAs for the base and InAlAs for the emitter and collector barriers, we have fabricated the first hot-electron transistor in this material system. We have shown that 1.6% of the injected hot electrons can be transported ballistically through a 0.3-μm-thick In0.53Ga0.47As plus 800-Å-thick InAlAs barrier layer at 77 K giving rise to an average mean free path of 920 Å. An energy spread of 130 meV was observed for the ballistic electrons injected at about 700 meV above the thermal equilibrium conditions. The values of collector barrier heights measured are in reasonable agreement with those deduced independently from thermionic emission studies in InGaAs gate, InAlAs/InGaAs capacitor structures.
Analytical solution for the lateral current distribution in multiple stripe laser diodes
Authors: Amann Markus-Christian , Kappeler Franz
Published: July 2002

The lateral profile of the injection current along the active layer in multiple stripe laser diodes is analyzed for the practical case of homogeneous current density within each individual stripe contact. By means of conformal mapping an exact analytical solution is found for arbitrary contact configurations (number, width, and location) driven with different currents. The simple form of the solution eases the analysis of modal gain and supermode discrimination in gain-guided and index-guided arrays of stripe-geometry laser diodes.
Electron beam stimulated nonthermal crystallization of CdS surface layers: Observations by real-time atomic-resolution electron microscopy
Authors: Ehrlich Daniel J. , Smith David J.
Published: July 2002

The transformations of partially amorphous CdS surfaces induced by 100–400 keV electrons have been followed in real time by atomic-resolution electron microscopy. A definite sequence of atomic rearrangements leading to nucleation and growth of CdS and Cd crystals was observed. These processes are believed to be due to nonthermal mechanisms involving inelastic electron collisions rather than direct knock-on collisions between electrons and the atomic nuclei since there is no threshold over the range of incident electron energies. These effects may be responsible for the degradation of electron beam pumped CdS lasers which has been reported elsewhere.
Nonlinear high-frequency response of GaAs metal-semiconductor field-effect transistors
Authors: Abeles J. H. , Tu C. W. , Schwarz S. A. , Brennan T. M.
Published: July 2002

Calculations show that phase nonlinearity in 1 μm gate length power GaAs metal-semiconductor field-effect transistors (MESFET’s) can be accounted for by the variation of gate-channel capacitance with gate bias voltage. Buried-layer GaAs MESFET’s having constant gate-channel capacitance have been fabricated and their high-frequency linearity measured. The devices display dramatic reductions of phase nonlinearity to 0.15°/W output power at 6 GHz for powers below saturation in 8 mm gate-width devices confirming that nonlinear capacitance causes nonlinearity observed in conventional GaAs MESFET’s. Channel transit time, estimated at 3–6 ps, is not significant as a cause of nonlinearity and varies less than 100 fs with signal level.
Resonant tunneling transport at 300 K in GaAs-AlGaAs quantum wells grown by metalorganic chemical vapor deposition
Authors: Ray S. , Ruden P. , Sokolov V. , Kolbas R. , Boonstra T. , Williams J.
Published: July 2002

Resonant tunneling transport was studied in GaAs-AlGaAs single well, double barrier structures. Negative differential resistance at 77 and 300 K was observed in devices grown by metalorganic chemical vapor deposition. The observed peak to valley ratios were 6 to 1 and 1.48 to 1, respectively. The presence of GaAs spacer layers was found to have a distinct effect on the 300 K current versus voltage characteristics. Microwave oscillation at frequencies up to 3.0 GHz was observed at 300 K. A short discussion of the oscillation frequency limits of our structure is presented.
Infrared absorption in PtSi-Si interface states
Authors: Flohr Th. , Schulz M.
Published: July 2002

Photoacoustic absorption and transmission measurements are performed to detect the contribution of interface states at the PtSi-Si interface to the absorption of the metal film. PtSi films on silicon substrates in the thickness range 27–420 Å are employed. The results are interpreted by a multilayer optical model. Absorption in an interface layer representing interface states is about 10%.
Distributions of hole and electron trapping centers in SiO2 film on Si, and the relation with the electrostatic tribo electrification phenomena of quartz
Authors: Iwamatsu S.
Published: July 2002

The details of the distribution of hole and electron trapping centers in SiO2 film on Si have been studied. Trapped holes are located and related mainly to excess silicon at the Si-SiO2 interface and trapped electrons are located and related mainly to excess oxygen at the SiO2 surface. By the friction tests of quartz samples, new electrostatic tribo electrification phenomena were found. By oxygen annealing, the trapping of quartz changes from positive to negative and by friction of the same type quartz samples, the surface changes show the same polarity. These results show that electro tribo electrification phenomena are related to surface hole and electron trapping states.
Superlattice GaAs mixed tunneling avalanche transit time device structure
Authors: Christou A. , Varmazis K.
Published: July 2002

A superlattice GaAs-Ga0.7Al0.3As mixed tunneling avalanche transit time device has been fabricated and tested at 94 GHz. Two superlattice regions are utilized in order to control the avalanche and the drift currents. The superlattice in the avalanche region enhances the electron ionization rate by a factor of 8, while the superlattice in the drift region maximizes the tunneling current. At 94 GHz, pulsed output power of 0.2–0.4 W was obtained.
Optoelectronic integrated AlGaAs/GaAs p-i-n/field-effect transistor with an embedded, planar p-i-n photodiode
Authors: Miura S. , Wada O. , Makiuchi M. , Nakai K.
Published: July 2002

A new planarization technique for fabricating an optoelectronic integrated circuit (OEIC) has been developed. A photodiode has been perfectly embedded in a semi-insulating GaAs substrate with a high uniformity over the wafer. A monolithically integrated p-i-n photodiode/field-effect transistor (FET) has been successfully fabricated by applying this technique. This result indicates that the present technique is promising for the application to fabricating not only p-i-n/FET but also larger scale OEIC receivers and transmitters.
Magnetostatic hole modes
Authors: Peuzin J. C. , Gay J. C.
Published: July 2002

This letter deals with the general concept of magnetostatic modes that are localized around cavities bored in an infinite ferromagnetic medium. The particular case of a circular hole of infinite length inside a material whose magnetization is parallel to the hole axis is studied in some detail. By using an original experimental configuration, it is shown that such a hole supports a very simple fundamental mode which is closely related to the well-known uniform precession of a ferromagnetic rod biased along its axis.
Characterization of the implantation damage in SiO2 with x-ray photoelectron spectroscopy
Authors: Ajioka Tsuneo , Ushio Shintaro
Published: July 2002

X-ray photoelectron spectroscopy (XPS) has been applied to characterize the damage introduced into SiO2 by ion implantation. By measuring the peak width of Si2p from SiO2 which corresponds to perturbation of the SiO2 network, good depth profiles of the damage have been obtained for implanted samples and subsequently annealed samples. The results show that the damage distributed more widely than that calculated from energy deposition and that the perturbation of the network is caused not only by radiation damage but also by the existence of impurities in the network. It has been found that the XPS method is effective to understand the atomic structure, and thus, electrical properties of SiO2.
InGaAsP distributed feedback multiquantum well laser
Authors: Dutta N. K. , Napholtz S. G. , Piccirilli A. B. , Przybylek G.
Published: July 2002

The fabrication and performance characteristics of 1.3 μm InGaAsP distributed feedback (DFB) lasers with multiquantum well (MQW) active layers are reported. The lasers are of the double channel planar buried heterostructure type and utilize a second order grating with a periodicity of ∼3900 Å for frequency selective feedback. The lasers have threshold currents in the range 25–35 mA at 30 °C and external differential quantum efficiencies of 0.2 mW/mA/facet at 30 °C. The temperature dependence of threshold current is characterized by a T0 value of 95–100 K. The lasers have been operated to an output power of 19 mW in a single frequency. The measured dynamic linewidth under modulation is a factor of 2 smaller than that for regular double heterostructure lasers. The lower temperature dependence of threshold current and smaller dynamic linewidth make real index guided InGaAsP DFB MQW active layer lasers attractive for many system applications.
Deposition of oriented zinc oxide on an optical fiber
Authors: Heffner B. L. , Khuri-Yakub B. T.
Published: July 2002

Techniques are described by which an oriented zinc oxide film is sputtered directly on one side of an 80-μm-diam fused silica single-mode optical fiber. A 4-GHz piezoelectric transducer incorporating this film demonstrates that the film is oriented. Evidence of acoustic waves in the fiber is given by the swept-frequency vector input impedance of the transducer. Acoustic transducers fabricated directly on a fiber produce fields focused on the fiber core for efficient acousto-optic interactions, making possible many new fiber-optic signal processing devices.
Luminescence of Ga1−xAlxAs/GaAs single quantum wells grown by liquid phase epitaxy
Authors: Kelting K. , Koehler K. , Zwicknagl P.
Published: July 2002

Low-temperature liquid phase epitaxy is used to grow Ga0.6Al0.4As/GaAs/Ga0.6Al0.4As single quantum wells. Photoluminescence (T=2 K) reveals well thicknesses from 7 to 2.4 nm. Micrographs show that the spatial origin of highly intense luminescence (T=300 K) is in the GaAs layer.
Field-dependent linewidths and photoluminescence energies in GaAs-AlGaAs multiquantum well modulators
Authors: Juang F-Y. , Singh Jasprit , Bhattacharya Pallab K. , Bajema K. , Merlin R.
Published: July 2002

Photoluminescence linewidths and transition energies have been measured in GaAs-AlGaAs multiple quantum wells with large (≥160 Å) barrier widths as a function of applied transverse electric field. The experimental data agree well with values calculated by using a recently developed variational technique. It is apparent that heterointerface roughness is the dominant line broadening mechanism. The emission intensity decreases rapidly with field, principally due to carrier tunneling at high fields. At 80 kV/cm a shift of 20 meV in the emission energy is observed.
Very high quality single and multiple GaAs quantum wells grown by chemical beam epitaxy
Authors: Tsang W. T. , Miller R. C.
Published: July 2002

High quality GaAs/AlxGa1−xAs single and multiquantum well heterostructures were grown for the first time by chemical beam epitaxy. Studies using low-temperature photoluminescence and excitation spectroscopy techniques show that on the average these samples are similar in quality to similar structures from this laboratory grown by molecular beam epitaxy (MBE) and in certain specific characteristics superior to the MBE ones. Furthermore, in some important respects, they are also superior to those grown by organometallic chemical vapor deposition (OMCVD). The very small red shifts observed between emission and n=1 exciton transition E1h with continuous growth show that the emission is dominated by E1h excitons. An interface roughness of δL≲±a/2, where a is the lattice constant, and very square wells (undistorted) even with continuous growth, in contrast to OMCVD are inferred from the excitation spectra. Unusually sharp exciton transition peaks up to E3h including forbidden transitions were obtained in single quantum wells. Such high quality line shape has not been obtained in MBE or OMCVD grown wafers so far. The excitation spectra also show no evidence of band filling due to holes or electrons from the AlxGa1−xAs layers which is a common problem with the OMCVD technique. From this study, it is also shown that the GaAs and AlxGa1−xAs materials are of very high purity.
Crosstalk of the dynamical dissipative behavior between different parts in a current-carrying semiconductor
Authors: Röhricht B. , Wessely B. , Parisi J. , Peinke J.
Published: July 2002

We have experimentally demonstrated the long-range crosstalk of transient chaotic behavior between separate parts of a single p-Ge crystal. Our experiments focused on the mutual coupling of the different intrinsic current oscillations generated in each part during the electric avalanche breakdown at liquid helium temperatures. Our results help to clarify the unwanted hot-carrier effects with respect to very large scale integration semiconductor circuits.
Absence of Fermi level pinning at metal-InxGa1−xAs(100) interfaces
Authors: Brillson L. J. , Slade M. L. , Viturro R. E. , Kelly M. K. , Tache N. , Margaritondo G. , Woodall J. M. , Kirchner P. D. , Pettit G. D. , Wright S. L.
Published: July 2002

Soft x-ray photoemission spectroscopy measurements of clean, ordered InxGa1−xAs (100) surfaces with Au, In, Ge, or Al overlayers reveal an unpinned Fermi level across the entire In alloy series. The Fermi level stabilization energies depend strongly on the particular metal and differ dramatically from those of air-exposed interfaces. This wide range of Schottky barrier height for III-V compounds is best accounted for by a chemically induced modification in metal-alloy composition.
Superior characteristics of nitridized thermal oxide grown on polycrystalline silicon
Authors: Chen Chiou-Feng , Wu Ching-Yuan
Published: July 2002

Polycrystalline silicon dioxide (poly-oxide) nitridized at high temperatures in ammonia ambient has been characterized by using ramp current-voltage (I-V) and constant current stressed voltage-time (V-t) measurements. It is found that the nitridized poly-oxide has less leakage current and stronger dielectric field strength as compared to conventional poly-oxide. These advantages are attributed to the slightly increased trapping effect and the less severe asperity effect of the nitridized poly-oxide. It has been shown that the nitridized poly-oxide is a good material for applications in high density electrically erasable and programmable read only memory (EEPROM) devices.
Ion beam irradiation of Langmuir–Blodgett polydiacetylene films
Authors: Elman B. S. , Blackburn Gary F. , Samuelson Lynne A. , Kenneson D. G.
Published: July 2002

Effects of ion beam irradiation of ≂100-nm-thick Langmuir–Blodgett polydiacetylene films have been investigated in the low-energy regime E<200 keV. Optical absorption and electrical resistivity measurements have been performed to characterize the modified materials. The results show that changes in optical and electrical properties associated with structural modifications are strongly correlated.
Growth of GaAs bicrystals
Authors: Cho N.-H. , Carter C. B. , Elgat Z. , Wagner D. K.
Published: July 2002

Bicrystals of gallium arsenide have been grown by the technique of organometallic, vapor phase epitaxy on substrates cut from Czochralski-grown germanium bicrystals. Both 〈110〉 and 〈001〉 tilt boundaries have been grown. Experimental illustrations of the Σ=3 and Σ=5 grain boundaries are presented. The grain boundaries tend to facet along well-defined planes but closely reproduce the misorientation of the seed bicrystal.
Theoretical study of electron mobility in a two-dimensional electron gas confined at a lattice-matched ZnSe-Zn(S,Te) heterointerface
Authors: Ruda H. E.
Published: July 2002

A strain-free ZnSe-Zn(S,Te): x≊0.37 heterointerface is proposed as an ideal structure for the confinement of a two-dimensional electron gas in ZnSe. The electron mobilities were calculated for this structure for the first time, including all major scattering mechanisms, and considering both intra- and inter-subband scattering processes. The dependence of the electron mobility at both 4.2 and 77 K on the areal density in the well was calculated. The peak inherent mobility limit was found to be about 3×105 and about 1×104 cm2/V s at 4.2 and 77 K, respectively.
Electrical characteristics of InAsSb/GaSb heterojunctions
Authors: Srivastava A. K. , Zyskind J. L. , Lum R. M. , Dutt B. V. , Klingert J. K.
Published: July 2002

Heterojunctions of n-type InAs0.95Sb0.05 grown by metalorganic chemical vapor deposition on n-type GaSb substrates were studied by capacitance-voltage and current-voltage measurements. The n-n heterojunctions are strongly rectifying and behave like metal-(n) GaSb Schottky diodes with a barrier height of 0.80±0.02 eV. These measurements establish that the band lineup in this system is of the broken gap variety. We measure the valence-band offset, Ev(GaSb)−Ev(InAs0.95Sb0.05), to be 0.67±0.04 eV.
Efficient stimulated Brillouin backscattering of multiple pulses in the highly transient regime
Authors: Greiner-Mothes M. A. , Witte K. J.
Published: July 2002

Stimulated Brillouin scattering in the highly transient regime is experimentally investigated using a multipulse reflection scheme. In high pressure N2 and SF6 backward pulses with reflection coefficients approaching 1 are demonstrated employing 1 ns pump pulses at 1.32 μm. The experimentally observed reflection behavior is satisfactorily reproduced by a numerical solution of the equations describing the scattering process. The phase conjugated fractions in the backscattered light is large.
Technique to produce coherent x-ray radiation via laser pumping of a relativistic ion beam
Authors: Bogacz S. A. , Ketterson J. B.
Published: July 2002

The level population of a beam of relativistic positive ions with Z≥2 having a single bound electron may be inverted by the application of a ‘‘π pulse’’ of laser radiation tuned to the Doppler-shifted 1s–2p transition. When the laser beam and ion beam move in opposite directions, the required laser frequency is reduced by a factor 2γ. Subsequently applied short wavelength resonant radiation moving in the same direction as the ion beam (with an inverted population) will be amplified via stimulated emission, the wavelength in the lab frame now being shorter than the original laser wavelength by a factor (2γ)2.
Behavior of inversion layers in 3C silicon carbide
Authors: Avila R. E. , Kopanski J. J. , Fung C. D.
Published: July 2002

A study on the field-induced surface-charge region in 3C silicon carbide (SiC) using 1 MHz capacitance-voltage (C-V) measurements at room temperature is here reported. A double column mercury probe was used on oxidized SiC substrates to form metal-oxide-semiconductor (MOS) structures. These structures were characterized in terms of the substrate doping profile, effective fixed oxide charge, and interface trap density. A distinctive feature of the MOS C-V curves from accumulation to inversion is that after going into deep depletion the capacitance rises to its equilibrium inversion level during the voltage sweep. Capacitance transient measurements indicate that the minority-carrier generation occurs at the SiO2/SiC interface.
Molecular beam epitaxial growth of a novel strained-layer superlattice system: CdTe-ZnTe
Authors: Monfroy G. , Sivananthan S. , Chu X. , Faurie J. P. , Knox R. D. , Staudenmann J. L.
Published: July 2002

CdTe-ZnTe strained-layer superlattices have been grown for the first time using the molecular beam epitaxy technique. The superlattices have been grown at 285 °C. They have been characterized by electron and x-ray diffraction. The presence of satellite peaks in the x-ray spectra shows that the superlattices are of excellent quality despite the large mismatch between CdTe and ZnTe along the growth axis (Δa/a=6.4%). X-ray oscillation patterns show that the superlattices are three-dimensional crystals.
Resonant tunneling through a double GaAs/AlAs superlattice barrier, single quantum well heterostructure
Authors: Reed M. A. , Lee J. W. , Tsai H-L.
Published: July 2002

Resonant tunneling has been demonstrated through a double barrier, single quantum well heterostructure in which the barriers have been replaced by thin, short period binary superlattices. The superlattice structure does not exhibit the asymmetry around zero bias in the electrical characteristics normally observed in the conventional AlxGa1−xAs barrier structures, suggestive of reduced roughness at the inverted interface by superlattice smoothing. The structure exhibits an anomalously low barrier height and a peak to valley tunnel current ratio of 1.8:1 at 300 K.
Laser induced enhancement in sensitivity of polymeric nuclear track detector CR-39
Authors: Kukreja L. M. , Joshi V. B. , Bhagwat A. M. , Chatterjee U. K. , Bhawalkar D. D.
Published: July 2002

It is found that the polymer CR-39 treated with a cw CO2 laser at a fluence between 13 and 30 J cm−2 shows enhancement in its track revelation sensitivity up to 1.6 times for the α particles and 1.8 times for the fission fragments from a 252Cf source.
Transport and persistent photoconductivity in InGaAs/InP single quantum wells
Authors: Anderson D. A. , Bass S. J. , Kane M. J. , Taylor L. L.
Published: July 2002

Hall effect and Shubnikov–de Haas data are presented for single 100 Å InGaAs/InP quantum wells grown by atmospheric pressure metalorganic chemical vapor deposition. Both modulation doped and nominally undoped structures are studied. Measurements are made on the latter structures by using the low-temperature persistent photoconductivity to put carriers into the quantum well. Mobilities as high as 95 000 cm2/V s have been achieved at carrier densities of 9×1011 cm−2. The persistent photoconductivity effect is also used to study the dependence of mobility on carrier density and the data are analyzed in terms of ionized impurity and alloy disorder scattering.
Residual acceptor assessment in as-grown bulk GaAs by Raman and selective pair luminescence spectroscopy: A comparative study
Authors: Wagner J. , Ramsteiner M.
Published: July 2002

Electronic Raman scattering and selective pair luminescence spectroscopy have been used to characterize residual acceptors in bulk-grown GaAs. Both techniques are compared by studying the same set of samples cut from undoped semi-insulating material. The Raman spectra from shallow acceptors were excited with the 1064-nm line of a neodymium:yttrium aluminum garnet laser as well as with an infrared dye laser at ∼860 nm. Raman scattering has the advantage of being a quantitative tool whereas selective pair luminescence spectroscopy is found to be more sensitive (detection limit ∼1×1014 acceptors/cm3). The latter technique is strongly facilitated by using an optical multichannel detection system. This study demonstrates that the combination of both techniques is necessary for the sensitive and quantitative characterization of residual acceptors in as-grown bulk GaAs.
cw operation of GaInAsSb/AlGaAsSb lasers up to 190 K
Authors: Caneau C. , Srivastava A. K. , Zyskind J. L. , Sulhoff J. W. , Dentai A. G. , Pollack M. A.
Published: July 2002

Continuous operation of 2.1 μm wavelength Ga0.84In0.16As0.15Sb0.85 /Al0.27Ga0.73As0.04Sb0.96 double heterostructure injection lasers has been achieved up to a temperature of 190 K for the first time. The laser wafers were grown by liquid phase epitaxy. In pulsed operation, broad area devices with active layer thicknesses of 0.8–1.0 μm exhibited room-temperature threshold current densities as low as 7 kA/cm2.
Observation of a negative differential resistance due to tunneling through a single barrier into a quantum well
Authors: Morkoç H. , Chen J. , Reddy U. K. , Henderson T. , Luryi S.
Published: July 2002

We have observed a negative differential resistance (NDR) in a single-barrier tunneling structure in which electrons tunnel from a doped semiconductor emitter layer into a quantum well (QW) layer and subsequently drift laterally to a specially designed contact. Pronounced NDR is seen already at room temperature and at 77 K the peak to valley (PTV) ratio in current is more than 2:1. Our results lend support to a recent hypothesis by Luryi [Appl. Phys. Lett. 47, 490 (1985)] that the NDR in double-barrier tunneling structures is not related to a resonant enhancement of the tunneling probability at selected electron energies, but rather originates from tunneling into a system of electron states of reduced dimensionality. For comparison we have also fabricated a QW structure with two tunneling barriers, in which the parameters of the emitter barrier and the QW are identical to those in the single-barrier structure. In the double-barrier structure we have obtained current densities as high as 4×104 A/cm2 and a NDR with PTV ratios of 3:1 at 300 K and 9:1 at 77 K.
Improved performance of XeF lasers in argon diluent
Authors: Kimura W. D. , Salesky E. T. , Seamans J. F.
Published: July 2002

A comparison of laser performance in electron beam pumped XeF using either neon or argon diluent is presented. Extraction measurements are performed at room temperature under high-energy loading conditions (160 kW/cm3, 1 μs laser pulse lengths) using either NF3 or F2 as halogen fuels. It is found with neon diluent that the laser output remains relatively constant during the excitation pulse, but with argon diluent the output increases almost linearly during the pulse. This continuous rise of the laser output with argon diluent leads to efficiencies higher than with neon diluent for input energy loadings ≳100 J/l. There are also indications that the argon diluent mixture is less susceptible to halogen burn-up.
Comment on ‘‘Mobility of Ni versus Zr in an amorphous Ni-Zr alloy’’ [Appl. Phys. Lett. 4
8, 517 (1986)]
Authors: Rothman S. J. , Averback R. S. , Hahn H.
Published: July 2002

Comments are made on Barbour’s paper concerning the mobility and diffusion of Ni and Zr in amorphous Ni−Zr alloys. Specifically, the method of Barbour et al. cannot, in principle, be used to determine which species moves faster. (AIP)
Severe loss of dopant activity due to CHF3+CO2 reactive ion etch damage
Authors: Mikkelsen J. C. , Wu I-W.
Published: July 2002

We report direct evidence from spreading resistance carrier profiling that an effective reduction of up to 5×1019 carriers cm−3 is caused by etching 10–150 nm of doped silicon with a CHF3+CO2 plasma in a commercial hexode reactor. During an 80-nm etch of bulk p+- and n+-Si, over 99 and 90% respectively of the carriers are trapped or complexed to a depth extending 200 nm from the etched surface. Thermal annealing at 450 °C restores all of the electrical activity, a behavior which is similar to the recovery of phydrogen-passivated acceptor impurities. More complicated behavior was observed for carrier deactivation of both p+ and n+ implanted junctions, where only partial recovery occurs after a 450 °C anneal. Further annealing at 850 °C does not reactivate any further p-type dopant, but a 950 °C anneal does increase the n-type dopant activity.
Passivation of deep level defects in molecular beam epitaxial GaAs by hydrogen plasma exposure
Authors: Dautremont-Smith W. C. , Nabity J. C. , Swaminathan V. , Stavola Michael , Chevallier J. , Tu C. W. , Pearton S. J.
Published: July 2002

The effect of hydrogen plasma exposure on the deep level defects present in GaAs grown by molecular beam epitaxy (MBE) has been investigated by deep level transient spectroscopy and by photoluminescence. The three commonly observed defects in MBE grown layers, the M1, M2, and M4 levels, found to be present at a total concentration of 5×1013 cm−3, are completely passivated by exposure to the hydrogen plasma. At low carrier concentration, in samples where surface recombination is suppressed by a thin GaxAl1−xAs cap, passivation of these defects increases photoluminescence efficiency by factors of 30 and 100 at 298 and 77 K, respectively. Defect passivation occurs in addition to the previously reported donor neutralization, but, whereas the latter is removed by a 400 °C, 5 min anneal, the former remains fully effective. Only upon 600 °C, 5 min annealing does the defect level passivation begin to be lost. Thus there is a wide temperature window within which it is possible to regain the carrier concentration without loss of passivation of the deep level defects.
Surface acoustic wave acousto-electro-optic effect
Authors: Das P. , Scholtz A. V. , Urillo A. J. , Litynski D. M. , Shklarsky D.
Published: July 2002

A new device which combines both acousto-optic and electro-optic effects in one integrated manner using surface acoustic wave technology has been implemented and offers unique advantages. In particular, this permits an additional input port for information which leads to compact implementation and simplified architecture in optical signal processing applications. The objective of this letter is to present some theoretical and experimental results in the Raman–Nath regime. These are found to agree over the range of investigation.
Effect of post-oxidation anneal on ultrathin SiO2 gate oxides
Authors: Arienzo Maurizio , Dori Leonello , Szabo Thomas N.
Published: July 2002

Ultrathin silicon oxide films 5–6 nm thick have been grown in a double-walled furnace and annealed in N2 and Ar at temperatures varying between 850 and 1100 °C. The breakdown field distribution obtained is very tight and centered above 11 MV/cm for as-grown oxides at 850 °C. The oxides that received a post-oxidation anneal (POA) at 1000 °C show a consistent improvement in breakdown field distribution and breakdown charge density as compared to the oxides annealed at lower temperatures. Furthermore, under high field current stress, oxides with a POA at 1000 °C show a positive voltage flatband Vfb shift, while oxides with POA at a temperature T<1000 °C show a negative Vfb shift. These results point out the efficacy of a high-temperature POA of 5–6 nm oxides on breakdown strength and on the reduction of some defects responsible for the positive charge trapping.
Optical time-of-flight investigation of ambipolar carrier transport in GaAlAs using GaAs/GaAlAs double quantum well structures
Authors: Hillmer H. , Mayer G. , Forchel A. , Löchner K. S. , Bauser E.
Published: July 2002

We propose a new all-optical time-of-flight method which provides transport properties like the average carrier velocity and diffusivity from measurements of the flight duration in semiconductor materials sandwiched between two quantum wells. The method is capable of very high spatial and temporal resolution and is demonstrated by time-of-flight experiments in GaAlAs.
Study of deep level centers at excited states in GaP by means of transient optical absorption spectroscopy
Authors: Shibata Hiromasa , Eshita Takeshi , Tanimura Katsumi , Itoh Noriaki , Hayashi Yoshikazu , Yoneda Kiyoshi
Published: July 2002

Transient optical absorption and luminescence induced by an electron pulse in n-type GaP and their changes induced by a subsequent laser pulse have been measured. It is shown that the decays of the optical absorption and of the luminescence induced by an electron pulse consist of a fast (F) component that decays within 1 ms and slow (S) components having a lifetime of about 10 ms. It is shown also that a laser pulse incident on the specimen after the F component is eliminated reduces the S component and produces the F component. The F component is ascribed to donor-acceptor recombination and the S component to annihilation of metastable centers.
Origin of the nonexponential thermal emission kinetics of D
X centers in GaAlAs
Authors: Calleja E. , Mooney P. M. , Wright S. L. , Heiblum M.
Published: July 2002

Direct evidence has been found, via hydrostatic pressure experiments, that the random distribution of Al and Ga atoms (alloy broadening) is the main cause of the nonexponential behavior of thermal emission processes from DX centers in Ga1−xAlxAs alloys (0.19≤x≤0.74). Isothermal single-shot emission transients at constant capacitance were used to measure the nonexponential behavior. Experimental values of the degree of nonexponentiality at ambient pressure, as a function of the Al content, are in good agreement with an alloy broadening model. When hydrostatic pressure up to 11 kbar is applied, the nonexponential behavior does not change, confirming its independence from variations in the conduction-band structure.
Power-dependent coupling and fast switching in distributed coupling to ZnO waveguides
Authors: Fortenberry R. M. , Moshrefzadeh R. , Assanto G. , Mai Xu , Wright E. M. , Seaton C. T. , Stegeman G. I.
Published: July 2002

A 20-fold decrease in the efficiency of prism coupling into low-loss ZnO waveguides was found with increasing incident power at 0.532 μm. All-optical switching in the temporal envelope of 10 ns laser pulses was interpreted theoretically in terms of an absorptive nonlinearity with a relaxation time much slower than the pulse width.
Large valence-band nonparabolicity and tailorable hole masses in strained-layer superlattices
Authors: Osbourn G. C. , Schirber J. E. , Drummond T. J. , Dawson L. R. , Doyle B. L. , Fritz I. J.
Published: July 2002

The two-dimensional, strain-induced light-hole masses in InGaAs strained-layer superlattices are shown to have large nonparabolicity contributions. Calculated hole masses agree with experimental values to within the 20% scatter. The results indicate that these tailorable hole masses could be useful tools for studying two-dimensional valence transport.
Chemical and electronic structure of InSb-CdTe interfaces
Authors: Mackey K. J. , Allen P. M. G. , Herrenden-Harker W. G. , Williams R. H. , Whitehouse C. R. , Williams G. M.
Published: July 2002

The microscopic interactions at heterojunctions formed between cleaned surfaces of InSb and CdTe have been investigated by low-energy electron diffraction and soft x-ray photoelectron spectroscopy. Layers of CdTe have been deposited on 1×1 (110) cleaved InSb and on c(2×8) (100) sputter cleaned and annealed surfaces, for various substrate temperatures. The valence-band offset has been measured and compared with theoretical predictions for layers deposited on room-temperature substrates. For layers deposited onto substrates at elevated temperatures typical of those employed in molecular beam epitaxial growth, the interface is complex and consists of a region rich in indium and tellurium, presumed to be indium telluride. The thickness of this layer is temperature dependent and may be several tens of angstroms.
Single-crystal, optical interference filters and integrated high reflector/photodiode using multilayers of GaP and GaAsxP1−x
Authors: Gourley P. L. , Biefeld R. M. , Zipperian T. E.
Published: July 2002

Using metalorganic chemical vapor deposition, we have produced single-crystal optical interference filters (high reflectors and antireflectors) with alternating quarter-wave thick layers (in the range 300–600 Å) of GaP and GaAsxP1−x. We have measured reflectance values from 0.08 to 0.90 at selected wavelengths from 460 to 750 nm. These filters have the unique feature that their design wavelength can be shorter than that corresponding to the energy band gap of the multilayer. In addition, we have produced an integrated optical detector in which a photodiode and an electrically active high reflector were grown sequentially in a single growth run. The spectral characteristics of the filters and integrated detector are reported here.
Effects of coherency strain on the band gap of pseudomorphic InxGa1−xAs on (001) InP
Authors: People R.
Published: July 2002

The effects of lattice mismatch induced coherency strain on the direct (Γ) band gap of InxGa1−xAs alloys for commensurate growth on (001) InP substrates are presented. It is found that the low-temperature (T≊2 K) band gap of the strained ternary varies between 1.0 and 0.48 eV for 0≤x≤1.0. The band-gap difference ΔEg between the strained ternary and cubic InP varies therefore between 0.42 and 0.94 eV. The partitioning of ΔEg between conduction and valence bands has yet to be determined for nonlattice-matched compositions (i.e., x≠0.53). In view of the large calculated variation in ΔEg it is anticipated that coherency strain may provide a means for tailoring band discontinuities in this technologically important materials system. Potential applications are briefly reviewed.
Synchrotron radiation-induced etching of a carbon film in an oxygen gas
Authors: Kyuragi Hakaru , Urisu Tsuneo
Published: July 2002

It was found that a carbon film in an oxygen gas is etched by irradiation of synchrotron radiation (SR). The etching rate was about 3 nm/min for a 100-mA ring current in an oxygen pressure of 26.7 Pa, and it increased in proportion to the square root of the oxygen pressure and the incident SR beam power. An analysis of the etched pattern indicates that the surface excitation induced by SR irradiation plays the predominant role in the described etching reaction.