bluuebunny/crossref_metadata_2025 huggingface dataset:
Mode-locked semiconductor lasers with gateable output and electrically controllable optical absorber
Authors: Tsang W. T. , Olsson N. A. , Logan R. A.
Published: February 2003

We proposed and demonstrated for the first time an electronically gateable mode-locked semiconductor laser capable of coding information on the picosecond optical pulses emitted. We further introduced an electronically controllable optical absorber which made it possible to electrically control the optical performance of the mode-locked semiconductor laser.
cw laser-annealing behavior of Se+-implanted InP investigated by ellipsometry
Authors: Mizuta M. , Merz J. L.
Published: February 2003

Damage removal of Se+-implanted InP after cw Ar+ laser annealing has been monitored by measurement of the optical extinction coefficient k. A gradual decrease in k as a function of laser power is observed for room-temperature ion-implanted InP samples, compared to a sharp decrease in k for ion-implanted Si. These data and electrical measurements indicate that the ion-implantation damage removal process for InP is more complex than for Si.
Simulation of backscattered electrons by reflection of primary electrons applied to optimization of detector designs
Authors: Brunner M.
Published: February 2003

A method has been developed to minimize the background signal of retarding field analyzers. It uses a negative electrode or negative charge on an insulator to reflect the beam of a scanning electron microscope towards the detector. This beam simulates backscattered electrons so that the response of the detector can be studied and optimized.
Properties and ion implantation of AlxGa1−xN epitaxial single crystal films prepared by low pressure metalorganic chemical vapor deposition
Authors: Khan M. A. , Skogman R. A. , Schulze R. G. , Gershenzon M.
Published: February 2003

High quality single crystal films of AlxGa1−xN have been grown on sapphire substrates using low pressure metalorganic chemical vapor deposition at 915 °C over the entire range of x. Electrical and optical properties of the layers were measured. Electrical compensation by Be+ and N+ implants in the layers was studied. Schottky barriers were fabricated and their current voltage characteristics were studied. We also report some initial results of a study of GaN growth kinetics.
Extremely rapid out diffusion of sulfur in InP
Authors: Chin A. K. , Camlibel I. , Sheng T. T. , Bonner W. A.
Published: February 2003

During sealed ampoule annealing of n-type (S,Se,Sn) InP crystals at 550 °C, an unexpected diffusion front was observed whose apparent diffusivity exceeded that of the rapidly diffusing Zn impurity by about two orders of magnitude. Using luminescence techniques, this diffusion front was correlated with changes in the ionized impurity level. In this letter, we show that for annealed InP:S (2×1018 cm−3) crystals the donor profile obtained from cathodoluminescence (CL) intensity measurements corresponds to the 34S profile obtained by secondary ion mass spectroscopy. Although dislocations are generally paths along which impurities can rapidly migrate, CL imaging shows that dislocations impede rather than enhance sulfur out diffusion. Further study is required to determine the rapid out-diffusion mechanism.
Photoluminescence of GaAs-AlxGa1−xAs multiple quantum well structure under high excitations
Authors: Xu Z. Y. , Kreismanis V. G. , Tang C. L.
Published: February 2003

Allowed transitions between the n=1, 2, and 3 subbands of the conduction and valence bands of a multiple quantum well heterostructure of GaAs-Al0.6Ga0.4As are seen in spontaneous emission under high excitations. The observed peaks agree very well with the calculated locations of the peaks when the finite depth of the potential well and the nonparabolicity of the conduction band are taken into account. The same basic features are seen under cw or picosecond pulse excitation and at room temperature, 77 K, or 4.2 K.
Hot-electron energy deposition around unsupported laser targets
Authors: Eidmann K. , Maaswinkel A. , Sigel R. , Witkowski S. , Amiranoff F. , Fabbro R. , Hares J. D. , Kilkenny J. D.
Published: February 2003

Free-falling spheres, released by a simple mechanism, are used as laser targets. Hot-electron energy transport upon one-sided irradiation with 300-ps iodine laser pulses (6×1015 W cm−2) is studied by various methods, including x-ray pinhole photography and time-resolved shadowgraphy. Spatial energy deposition is consistent with hot-electron spreading in the presence of self-generated magnetic fields, as suggested by recent experiments and simulations. The insensitivity of the results to the presence of a supporting stalk is attributed to inductive decoupling of the target. Free-falling targets open the possibility of highly symmetric implosion experiments.
Kinetics of interstitial supersaturation during oxidation of silicon
Authors: Hu S. M.
Published: February 2003

The kinetics of the supersaturation of self-interstitials during the thermal oxidation of silicon is reexamined by considering a finite diffusivity of these interstitials. The rate of interstitial generation is assumed to be proportional to the rate of oxidation, and the rate of surface annihilation is assumed to be a first order reaction. The result from an analytical solution shows that within a reasonable oxidation time span, a suitable power-law kinetics is obtained, with an exponent that falls within the range of most of the reported experimental values.
Time-resolved nonlinear luminescence spectroscopy by picosecond excitation correlation
Authors: Jo/rgensen M. , Hvam J. M.
Published: February 2003

A time-resolved nonlinear luminescence spectroscopy based on a picosecond excitation correlation technique is described. It has been used to determine the recombination lifetimes of free and bound excitons in CdSe at low temperature and low exciton density.
Heteroepitaxial growth of CdTe on GaAs by laser assisted deposition
Authors: Cheung J. T. , Khoshnevisan M. , Magee T.
Published: February 2003

The heteroepitaxial growth of (111) CdTe on (100) GaAs substrates has been obtained by laser assisted deposition at 350 °C. Films 5–14 μm thick were characterized by x-ray diffraction, UV reflectance measurement, and transmission electron microscopy. Results indicate good crystallinity with 105 cm−2 dislocation densities beyond a few microns from the CdTe/GaAs interface.
Broadly tunable mode-locked HgCdTe lasers
Authors: Putnam R. S. , Salour M. M. , Harman T. C.
Published: February 2003

We report tunable cw mode-locked laser action from synchronously pumped HgCdTe lasers. 4–8-μm-thick liquid phase expitaxial layers lasing at λ=1.2 and λ=1.73–2.0 μm are longitudinally pumped by a neodymium: yttrium aluminum garret (Nd:YAG) laser. Peak output powers of 50 W using a chopped pump beam, and a cw mode-locked average output power of 5.6 mW, have been achieved at a wavelength of 1.2 μm. Nearly bandwidth-limited pulses of 6-ps duration have also been obtained. Tuning from λ=1.82 to 2.0 μm via the Burstein–Moss shift has been accomplished on a single epilayer by varying the loss in the external cavity.
Modification of optical properties of GaAs-Ga1−xAlxAs superlattices due to band mixing
Authors: Chang Yia-Chung , Schulman J. N.
Published: February 2003

A theoretical calculation of the optical properties of GaAs-Ga1−xAlxAs superlattices is presented. The calculation includes the detailed atomic nature of the superlattice electronic states in a realistic tight-binding model. It is found that the mixture of the bulk heavy hole and light hole states in the superlattice wave function substantially affects the optical properties.
Optical studies of InxGa1−xAs-GaAs strained multiquantum well structures
Authors: Marzin J. Y. , Rao E. V. K.
Published: February 2003

We present photoluminescence and absorption measurements on molecular beam epitaxy grown strained InxGa1−xAs-GaAs multiquantum well structures. The absorption results are interpreted as excitonic transitions (n=1, n=2), while the room-temperature luminescence spectrum shows the corresponding subband to subband transitions, and the low-temperature luminescence spectrum exhibits only the n=1 excitonic line.
Characteristic electronic defects at the Si-SiO2 interface
Authors: Johnson N. M. , Biegelsen D. K. , Moyer M. D. , Chang S. T. , Poindexter E. H. , Caplan P. J.
Published: February 2003

On unannealed, thermally oxidized silicon, electron spin resonance reveals an oriented interface defect which is termed the Pb center and identified as the trivalent silicon defect. Deep level transient spectroscopy (DLTS) reveals two broad characteristic peaks in the interface-state distribution: one ∼0.3 eV above the silicon valence-band maximum and a second ∼0.25 eV below the conduction band. Isochronal anneals of oxidized silicon, coated with aluminum, show that the spin density and the densities of the two DLTS peaks have the same annealing kinetics. On large-area, Al-gated capacitors the spin density can be modulated with an applied voltage; sweeping the silicon band gap at the interface through the Fermi level reveals that the spin density is approximately constant over the central region of the band gap but decreases near the band edges. The variation of the spin density with gate voltage identifies an amphoteric center with both electronic transitions in the band gap. Both the annealing behavior and the voltage dependence of the Pb center support the conclusion that these transitions correspond to the two characteristic peaks in the interface-state distribution. The ∼0.6 eV separation of the peaks is the effective correlation energy of the dangling orbital on a trivalent silicon defect at the Si-SiO2 interface. The similarity between the disordered interface and amorphous silicon is discussed.
Surface plasmon emission in metal-insulator-degenerate p-type semiconductor structures
Authors: Whiteley S. R. , Xie L. Z. , Hemphill R. , Gustafson T. K.
Published: February 2003

The complex dispersion relation for the antisymmetric plasmon mode in the presence of the tunneling interaction in In-In2O3-SnTe tunnel junctions is solved numerically. Net amplification of the mode may be possible at submillimeter and far infrared wavelengths in cooled junctions.
Phase-locked semiconductor laser array with separate contacts
Authors: Katz J. , Kapon E. , Lindsey C. , Margalit S. , Shreter U. , Yariv A.
Published: February 2003

A new monolithic phase-locked semiconductor laser array has been fabricated. Employing two-level metallization, each of the eight elements in the array has a separate contact, thus making it possible to compensate for device nonuniformities and control the near-field and far-field patterns. Threshold currents are approximately 60 mA for each 5-μm-wide laser in the array. Phase locking has been observed via the narrowing of the far-field pattern. Experimental results are compared to those obtained from the same arrays operated with all the lasers connected in parallel.
Study of the uniformity and stoichiometry of CoSi2 films using Rutherford backscattering spectroscopy and scanning electron microscopy
Authors: Ishibashi Kouichirou , Furukawa Seijiro
Published: February 2003

Uniformity and stoichiometry of solid phase epitaxial CoSi2 films were investigated by Rutherford backscattering spectroscopy (RBS) and scanning electron microscopy (SEM). In a series of samples, small deviations of the composition ratio from the silicide stoichiometry were always observed in the RBS spectra for the films. Furthermore, it was found from SEM observation that these films were not uniform and the surfaces of the samples consisted of two kinds of materials. From these results and the spectra of micro Auger electron spectroscopy, it was concluded that the surfaces of the samples consisted of a stoichiometric CoSi2 region and exposed Si regions.
Computer simulation of high speed melting of amorphous silicon
Authors: Webber H. C. , Cullis A. G. , Chew N. G.
Published: February 2003

The laser melting of amorphous Si is accurately modelled by computer calculations. It is found that the thermal conductivity of the amorphous phase must be set at approximately 10−2 W/cm K, a value much lower than that of crystalline material to obtain close agreement with experimental measurements. This low value is, however, consistent with the thermal conductivities of other amorphous materials. The results of the computations, when compared with experimental observations, confirm that the melting point of ion implanted amorphous Si is below that of crystalline Si, with a best estimate in the range 1185–1385 K.
Effect of thermal nitridation processes on boron and phosphorus diffusion in 〈100〉 silicon
Authors: Fahey P. , Dutton R. W. , Moslehi M.
Published: February 2003

The effect of the silicon thermal nitridation processes, nitridation of SiO2 (oxynitridation), and direct nitridation of the silicon surface on boron and phosphorus diffusion is examined. It is found that oxynitridation results in enhanced diffusion of both impurities while direct nitridation of the silicon surface causes retarded diffusion for both. These phenomena are explained by the mechanisms of silicon self-interstitial injection in the case of oxynitridation and self-interstitial depletion in the case of direct nitridation.
Thermal nitridation of silicon in nitrogen plasma
Authors: Nakamura H. , Kaneko M. , Matsumoto S. , Fujita S. , Sasaki A.
Published: February 2003

Direct thermal nitridation of silicon in a nitrogen plasma has been performed above 1000 °C. From Auger electron spectroscopy analysis, the formed films contain some oxygen and are identified as oxynitride films. Refractive indices of these films varied from 1.5 to 1.9 with nitridation time. The film thickness is about 40 Å after nitridation of 10 h at 1145 °C and the film growth is saturated at this value. Capacitance-voltage characteristics of Al gate metal-nitride-semiconductor capacitors show a stable behavior. The fixed charge density Qss is estimated to be on the order of 1012 cm−2.
Photoelectrochemical etching of integral lenses on InGaAsP/InP light-emitting diodes
Authors: Ostermayer F. W. , Kohl P. A. , Burton R. H.
Published: February 2003

A photoelectrochemical method has been developed for etching integral lenses on light-emitting diodes (LED’s). An LED wafer is immersed in an electrolyte and biased at a potential at which the etch rate is directly proportional to light intensity. The image of a photomask is projected onto the surface of the wafer to produce a spatial variation of light intensity to etch the desired shape. The method has been used to etch spherical lenses on the n-InP substrates of InGaAsP/InP LED’s. Extremely smooth surfaces are obtained for etch rates ≲0.5 μm/min. The resulting lensed LED’s gave the theoretically expected improvement in the light coupled into an optical fiber, indicating that the scattering loss of the lenses was very small. The technique is compatible with the standard LED processing and the apparatus required is relatively simple.
New types of high efficiency solar cells based on a-Si
Authors: Hamakawa Yoshihiro , Fujimoto Kouha , Okuda Kouji , Kashima Yoshio , Nonomura Shuichi , Okamoto Hiroaki
Published: February 2003

Three types of new structure a-Si solar cells having more than 9% efficiency are presented. The first one has a high optical reflection back electrode metal alloyed with optically transparent n-type μc-Si deposited on the conventional glass substrate a-SiC/a-Si heterojunction solar cell. The second type structure is an inverted p-i-n solar cell having Ag/TiO2/a-Si metal-insulator-semiconductor type back surface electrode which more efficiently collects longer wavelength photocarriers just above the band edge. The third structure demonstrated here has a-Si/polycrystalline tandem junction to pick up the energy of longer wavelength photons passing through the front side of the a-Si solar cell. All key technologies proposed here are practical and offer more promised real alternatives for the fabrication of high efficiency a-Si solar cells.
Bandwidth-limited picosecond pulse generation in a synchronously pumped GaAs laser containing a variable absorber diode
Authors: Stallard W. A. , Bradley D. J.
Published: February 2003

We report combined active and passive mode locking of an external cavity semiconductor laser containing one absorbing and one gain diode. Compared with active mode locking alone this method requires less critical tuning of the rf modulation frequency and is not limited to operation close to threshold. Colliding pulse mode locking is achieved by placing the absorber diode at one end of the cavity so as to increase the effective absorber cross section. Streak camera measurements show that the pulse trains are free from background noise and that the 30-ps pulses are bandwidth limited with sech2 profiles.
Selected area growth of InP by low pressure metalorganic chemical vapor deposition on ion implanted InP substrates
Authors: Favennec P. N. , Salvi M. , Di Forte Poisson M. A. , Duchemin J. P.
Published: February 2003

InP deposition by metalorganic chemical vapor deposition on implanted substrates has different qualities according to the damage density of the substrate surface induced by the bombardment. For low damage densities, the layer deposited is monocrystalline. For middle damage densities, the deposition is composed of nuclei. For high damage densities, there is no deposition on the implanted surface, and in this case, we observe a material transport. By using the ion implantation technique in conjuntion with metalorganic chemical vapor deposition, it is possible to have selective area growth of InP.
Stress compensation in laser diodes
Authors: Koyama H. , Nishioka T. , Isshiki K. , Namizaki H. , Kawazu S.
Published: February 2003

Stress compensation in GaAs-(Ga,Al)As laser diodes is discussed. The stress distributions in the laser diodes are theoretically simulated by the finite element method. The photoelastic effect is used to observe the actual strain fields. It is found by simulation that the stress can be minimized by optimizing the Si submount thickness. Lasers fabricated with the optimized submount successfully exhibit low strain fields.
Efficient discharge pumping of an XeCl laser using a high-voltage prepulse
Authors: Long William H. , Plummer Michael J. , Stappaerts Eddy A.
Published: February 2003

A laser efficiency of 4.2% at 4.2-J output has been obtained from a self-sustained discharge-pumped XeCl laser using a novel high-voltage prepulse technique to provide efficient energy transfer from a low-impedance transmission line to the load. High-pressure discharge-pumped lasers now offer a reliable, efficient, and scalable alternative to e beams for many applications in the visible and ultraviolet regions of the spectrum.
Ion-assisted deposition of bulklike ZrO2 films
Authors: Martin P. J. , Netterfield R. P. , Sainty W. G. , Clark G. J. , Lanford W. A. , Sie S. H.
Published: February 2003

Stable thin films of zirconium dioxide are produced by ion-assisted electron beam deposition at room temperature and 300 °C. The method yields films with substantially increased packing density resulting in refractive indices close to the bulk value. The improvement in optical properties is accompanied by an amorphous to cubic crystalline transition of the film structure which is mixed with a monoclinic phase for heated films.
Generation of tunable single-mode picosecond pulses from an AlGaAs semiconductor laser with grating feedback
Authors: Lundqvist S. , Andersson T. , Eng S. T.
Published: February 2003

Widely tunable single-mode picosecond pulses have been obtained from a buried optical guide AlGaAs semiconductor laser operated with external grating feedback. Intensity autocorrelation measurements show single-mode 30-ps pulses. A tuning range of 20 nm, corresponding to more than 70 different laser frequencies, was easily achieved.
Real-time measurement of picosecond optical pulses from an InGaAsP diode laser using an ultrafast streak camera with infrared frequency up-conversion
Authors: Onodera Noriaki , Ito Hiromasa , Inaba Humio
Published: February 2003

A novel method for real-time measurement of ultrashort optical pulses generated from InGaAsP diode lasers at the wavelength of 1.3 μm has been realized by means of an ultrafast streak camera incorporating a frequency up-conversion technique with a LiIO3 crystal pumped by a Q-switched neodymium: yttrium aluminum garnet (Nd:YAG) laser at 1.064 μm. The optical pulse from an InGaAsP double-channel planar buried heterostructure (DC-PBH) diode laser operated by a short pulse current of 1-ns duration was measured to have a full width at half-maximum (FWHM) of approximately 28 ps by single shot scanning with the temporal resolution of 8 ps. Using a 15-mm-long LiIO3 crystal and 500-W peak power of the pumping laser pulse focused at 400 μm in diameter, the up-conversion efficiency and minimum detectable peak power of the diode laser pulse at 1.3 μm were estimated to be approximately 0.65% and 1 mW, respectively. This technique can be widely utilized for real-time detection of ultrashort optical pulses in the wavelength range beyond 1–10 μm or more.
Ablation and lateral energy transport in high-Z plasmas produced by lasers
Authors: Gupta P. D. , Naik P. A. , Pant H. C.
Published: February 2003

A comparative study of ablation from moderate and high-Z layered targets of aluminum and gold in the laser intensity range 1011–1013 W/cm2 of a neodymium glass laser is presented. A substantially large lateral energy loss for high-Z target is observed from measurements of ablation depth, x-ray emission, and plasma blow-off.
Optical properties of GaInAs/AlInAs single quantum wells
Authors: Welch D. F. , Wicks G. W. , Eastman L. F.
Published: February 2003

Ga0.47In0.53As/Al0.48In0.52As single quantum wells grown by molecular beam epitaxy have exhibited photoluminescence emission from 9668 Å to the 1.55-μm bulk emission at 4 K. The emission at 9668 Å is 0.474 eV above the band gap of GaInAs. The single quantum well (SQW) is 15 Å wide which is the narrowest SQW reported in any III-V compound. The effect of varying the buffer layer of the SQW on the photoluminescence intensity of a 65-Å single quantum well is studied.
Plastic-deformation-induced deep level in GaP
Authors: Iqbal M. Zafar
Published: February 2003

Thermally stimulated current measurements on Schottky barriers evaporated on bent GaP:N epitaxial layers are reported. A pronounced peak corresponding to a deep level with a binding energy of ∼0.57 eV is attributed to dislocations produced during plastic deformation.
Modified palladium metal-oxide-semiconductor structures with increased ammonia gas sensitivity
Authors: Winquist F. , Spetz A. , Armgarth M. , Nylander C. , Lundström I.
Published: February 2003

It is known that palladium metal-oxide-semiconductor (Pd-MOS) structures are sensitive detectors for hydrogen gas. We show that the evaporation of a thin film of catalytically active metals on top of the structure can increase the sensitivity towards ammonia considerably. It was found that the thin metal must be in contact with the oxide to cause the increased sensitivity. The largest increase was observed with the transition metals Ir and Pt. The ammonia sensitivity could be enhanced about 60 times compared to that of an unmodified structure
High gain signal amplification in an InSb transphasor at 77 K
Authors: Tooley F. A. P. , Smith S. D. , Seaton C. T.
Published: February 2003

We present experimental observations of the variations of the input-output characteristic of a nonlinear Fabry–Perot resonator as a function of initial detuning. The characteristics include regions with various differential gains, or show hysteresis with the width of the bistable region being variable. Operating the device as a transphasor (optical transistor), a signal of 3 μW can be amplified with a signal power gain of up to 104 with the device operating at 77 K and 1819 cm−1.
Phase matching in frequency mixing with internally generated waves
Authors: Rustagi K. C. , Mehendale S. C. , Gupta P. K.
Published: February 2003

When some of the input waves involved in nonlinear frequency conversion are amplified internally, the phase mismatch is shown to reduce the conversion efficiency significantly even when Maker fringes are washed out.
Fast relaxing absorptive nonlinear refraction in superlattices
Authors: Yuen S. Y.
Published: February 2003

Two nonlinear optical processes in superlattices are studied. The first involves free-carrier absorption and the second involves direct intersubband absorption. The optical field modulates the energy-dependent effective mass or the distribution of electrons among the subbands, giving rise to nonlinear refraction. These processes have picosecond relaxation times and nonlinearities up to four orders of magnitude larger than the nonlinear refractive effects in bulk crystals with comparable relaxation times.
Direct observation of dislocation effects on threshold voltage of a GaAs field-effect transistor
Authors: Miyazawa Shintaro , Ishii Yasunobu , Ishida Satoru , Nanishi Yasushi
Published: February 2003

The threshold voltage of a GaAs metal-semiconductor field-effect transistor (MESFET) fabricated on a liquid encapsulated Czochralski grown, semi-insulating substrate was found to be influenced by growth-induced dislocations. Field-effect transistors located at less than 20–30 μm from a dislocation exhibited a threshold voltage lower than that of FET’s located far from a dislocation. The maximum difference in threshold voltage of FET’s located at less than and more than this critical distance was obtained to be about 300 mV. The first definitive correlation between dislocations and FET threshold voltage is reported.
Measurements of threshold carrier density of III-V semiconductor laser diodes
Authors: Su C. B. , Olshansky R.
Published: February 2003

A simple and accurate method is described for measurements of the carrier density at lasing threshold in double heterostructure diode lasers. The carrier densities measured are compared with those deduced from differential carrier lifetime measurements. Excellent agreement is obtained for the two independent methods.
Direct observation of lattice distortion in a strained-layer superlattice
Authors: Brown J. M. , Holonyak N. , Ludowise M. J. , Dietze W. T. , Lewis C. R.
Published: February 2003

The structure of strained-layer quantum well heterostructures grown by metalorganic chemical vapor deposition has been examined using both conventional and high resolution electron microscopy. It has been possible to show that the lattice mismatch in superlattice systems containing strain of up to 7.1×10−3 is accommodated by the introduction of a tetragonal expansion and compression of the lattice of successive layers. This can be seen in the splitting of the (001) spots in the electron diffraction pattern and by the bending of (111) lattice fringes at the heterojunction interfaces.
High photoconductivity in magnetron sputtered amorphous hydrogenated germanium films
Authors: Rudder R. A. , Cook J. W. , Lucovsky G.
Published: February 2003

Undoped amorphous hydrogenated germanium films which exhibit photoconductivities greater than 10−6 (Ω cm)−1 at a 1.96-eV photon flux of 1015 photons/(cm2 s) with corresponding mobility lifetime products of 10−6 cm2/V have been grown by magnetron sputtering. The films were also characterized by measuring the infrared absorption, the optical obsorption, and the dark conductivity as a function of temperature.
Graded collector heterojunction bipolar transistor
Authors: Chiu L. C. , Harder Ch. , Margalit S. , Yariv A.
Published: February 2003

A graded collector heterojunction bipolar transistor is proposed. The graded collector improves device speed performance at high current densities by reducing the influence of the Kirk effect.
Effects of As+ ion implantation on the Raman spectra of GaAs: ‘‘Spatial correlation’’ interpretation
Authors: Tiong K. K. , Amirtharaj P. M. , Pollak F. H. , Aspnes D. E.
Published: February 2003

We have studied Raman scattering from 〈100〉 GaAs samples implanted with 270-keV As+ ions with various fluences up to 3.2×1014 cm−2. In addition to phonon density of states effects, we observe a softening and asymmetric broadening of the allowed LO phonon while the small symmetry forbidden TO phonon remains almost unchanged. The behavior of the LO and TO modes can be explained quantitatively on the basis of a ‘‘spatial correlation’’ model related to q-vector relaxation induced by the damage. Our interpretation is quite general and makes it possible to use Raman spectra to evaluate an average size of undamaged regions in semiconductors.
Optical heating of electron-hole plasma in silicon by picosecond pulses
Authors: Lompré L.-A. , Liu J.-M. , Kurz H. , Bloembergen N.
Published: February 2003

Using a novel three-pulse technique, essential information about the density, optical effective mass, and kinetics of laser-generated plasmas in silicon has been obtained.
Ion mixing of markers in SiO2 and Si
Authors: Barcz A. J. , Paine B. M. , Nicolet M-A.
Published: February 2003

The amount of atomic mixing in amorphous SiO2 and Si is studied by measuring the redistribution of thin metal markers due to irradiation with 300-keV Xe+ ions. In SiO2, the mixing efficiency appears to be independent of the chemical nature of marker atoms and can be explained in terms of a linear cascade model. In Si, the mixing is found to correlate with thermally activated diffusivities of the marker species.
Structural evolution of very thin silicon oxide films during thermal growth in dry oxygen
Authors: Agius B. , Rigo S. , Rochet F. , Froment M. , Maillot C. , Roulet H. , Dufour G.
Published: February 2003

We have studied the structural characteristics of very thin silicon oxide films thermally grown (at 930 °C, 10 Torr) in 18O enriched dry oxygen for times ranging from 0.5 to 22.5 h (corresponding to equivalent thicknesses ranging from 3.2 to 20.8 nm). Chemical etching combined with nuclear microanalysis, x-ray photoelectron spectroscopy (XPS), and reflection high-energy electron diffraction (RHEED) has been applied to the samples. A layer that is very slow to dissolve (of equivalent thickness ∼1.1 nm) was observed for oxide films grown for oxidation times of less than 1 h (equivalent thicknesses under 4.6 nm). As indicated by XPS this layer seems to be related to a structure different from what is observed for thicker films; its existence is also correlated to a structural order as seen by RHEED.
Observation of Si2 in a chemical vapor deposition reactor by laser excited fluorescence
Authors: Ho Pauline , Breiland William G.
Published: February 2003

For the first time an intermediate chemical species, Si2, has been observed in the gas phase during the chemical vapor deposition of silicon from silane. This observation is inconsistent with previous theoretical models for silicon deposition, which assume that either thermodynamic equilibrium or surface kinetics determines the silicon deposition rate. It is consistent with the predictions of a new model for chemical vapor deposition by Coltrin et al., in which gas phase chemical kinetics play an important role in the deposition mechanism. The Si2 molecule could be a precursor to the nucleation of silicon particulates in the gas phase.
Blocking of threading dislocations by Hg1−xCdxTe expitaxial layers
Authors: James T. W. , Stoller R. E.
Published: February 2003

The process by which threading dislocations present in the substrate are bent into the interface plane during epitaxial layer growth and thus are blocked from propagating into the epitaxial layer has been observed in growth of the II-VI ternary alloy Hg1−xCdxTe on CdTe and Cd1−zZnzTe substrates. Stereo-pair transmission electron micrographs were analyzed which clearly revealed the interfacial dislocations to be in a planar network, as has been previously reported for III-V epitaxial systems in which the blocking mechanism has been identified by other investigators. Additional evidence of the blocking phenomenon has been provided by chemical dislocation-revealing etching, which verified that the substrate dislocations were not present in the layer.
Poling behavior of polyvinylidene fluoride at room temperature
Authors: Mopsik F. I. , DeReggi A. S.
Published: February 2003

The electrical polarization distribution for biaxially oriented polyvinylidene fluoride poled at room temperature was measured by means of the thermal pulse experiment. The evolution of the distribution as a function of poling field and poling time was studied. The resolution was one-tenth the sample thickness. In addition, the sample poled to the highest field was reverse poled to successively higher fields to study the effects of field reversal. The film was found to pole easiest in the middle regions implying a higher coercive field near the surfaces.
Compensation effects in Si-doped GaAs grown by molecular beam epitaxy
Authors: Nottenburg R. , Bühlmann H. J. , Frei M. , Ilegems M.
Published: February 2003

The effect of varying As4/Ga flux ratio during growth on the incorporation of Si as a dopant in GaAs grown by molecular beam epitaxy (MBE) has been studied by low-temperature mobility and carrier concentration measurements. In the low residual doping range (n≤1×1015 cm−3), electron mobilities increase with increasing As4 flux; this increase may be related to the reduced incorporation of compensating C acceptors. Highest mobility achieved was μ(55 K)=97 600 cm2/Vs at a background pressure of ∼2×10−6 Torr. At Si doping levels ≥1016 cm−3, both carrier concentration and mobility were found to be independent of As4 pressure over the range of our experiments ( pAs4 ∼0.9–6×10−6 Torr). We conclude, contrary to previous findings, that Si autocompensation effects have only a minor influence on the electrical properties of MBE GaAs layers under the usual growth conditions.
Carbon in semi-insulating, liquid encapsulated Czochralski GaAs
Authors: Hunter A. T. , Kimura H. , Baukus J. P. , Winston H. V. , Marsh O. J.
Published: February 2003

We have investigated undoped, semi-insulating GaAs, grown by the liquid encapsulated Czochralski technique in pyrolytic BN crucibles. The concentration of carbon, the principal shallow acceptor, depends on the water content of the B2O3 encapsulant. Dry B2O3 (100–150 ppm H2O) results in carbon concentrations as high as 8×1015 cm−3, while wet B2O3 (500 ppm H2O) results in carbon concentrations below the detection limit of 3–5×1014 cm−3. In samples with carbon below 5×1014 cm−3, the compensation (acceptors minus donors shallower than EL2) is also low, and the room-temperature carrier concentration can exceed 1011 cm−3. For samples with carbon above 5×1014 cm−3, the room-temperature carrier concentration is below 5×107 cm−3 for all samples measured. The compensation is less than the carbon concentration in high carbon samples, indicating that donors shallower than EL2 are significant in determining the value of the compensation in these samples.
Reduction of interface states in Pt-GaAs buried Schottky barrier
Authors: Onuma Takeshi , Uenoyama Takeshi , Yagita Hideki
Published: February 2003

The interface states of Pt-GaAs Schottky barrier were investigated by deep level transition spectroscopy. The concentrations of ∼0.46 eV deep electron trap located near the Schottky barrier interface were reduced by sintering Pt-GaAs. The interface of the buried Pt-GaAs Schottky barrier was improved by the Pt-GaAs reaction.
Localization induced electron-hole transition rate enhancement in GaAs quantum wells
Authors: Christen J. , Bimberg D. , Steckenborn A. , Weimann G.
Published: February 2003

The transition rate of excitonic e-h recombination in GaAs quantum wells is found to increase by almost one order of magnitude upon a decrease of the well width from infinity to 52 Å due to increased excitonic localization. Competing capture of free carriers by impurities is increasingly suppressed. Time delayed cathodoluminescence spectra and decay times taken at 5–300 K show this unambiguously. Transfer of carriers from 176-Å Ga0.6Al0.4As cladding wells is found to occur ballistically in 10−13 s.
Time-resolved measurement of hole sweepout in a GaAs photoconductor
Authors: Von Lehmen A. , Ballantyne J. M.
Published: February 2003

A nonlinear luminescence technique is used to measure hole sweepout in a GaAs photoconductor at room temperature. The measured sweepout time for an applied field of 20 kV/cm corresponds to an average hole velocity of 2.0×106 cm/s. A simple model for extracting the photoexcited population decay from the experimental data is described.
Interdigitated Al0.48In0.52As/Ga0.47In0.53As photoconductive detectors
Authors: Chen C. Y. , Pang Y. M. , Alavi K. , Cho A. Y. , Garbinski P. A.
Published: February 2003

We report a high performance interdigitated Al0.48In0.52As/Ga0.47In0.53As heterostructure photoconductive detector for high bit-rate, single-mode telecommunication applications. The detector shows a rise time of 80 ps, a fall time of 1.2 ns, and a peak responsivity seven times better than that of a pin photodiode. Our study shows that the long fall time is due to a slow minority-carrier (hole) drift velocity coupled with a two-dimensional effect. We have also tested the demodulation characteristics of the detector at frequencies as high as 2.7 GHz. Furthermore, we have investigated the noise properties of the detector in the frequency band of 100 MHz–1.1 GHz.
Fermi energy pinning behavior and chemical reactivity of the Pd/GaAs (110) interface
Authors: Kendelewicz T. , Petro W. G. , Pan S. H. , Williams M. D. , Lindau I. , Spicer W. E.
Published: February 2003

The room-temperature growth of the Pd/n-GaAs (110) intimate interface has been studied by soft x-ray core level photoemission spectroscopy. It is shown that Pd reacts with the GaAs surface forming an arsenide compound in which phase segregated Ga metal is included. In addition some As is segregated on the surface of this composite. Using deconvolution of the different core level contributions, the Schottky barrier height of this system is experimentally determined to be 0.9±0.05 eV. The pinning is attributed to the deeper level of the unified defect model.
Effect of temperature gradients on the first-order Raman spectrum of Si
Authors: Raptis J. , Liarokapis E. , Anastassakis E.
Published: February 2003

We report the results of measurements of the first-order Raman spectrum of Si under conditions of large temperature inhomogeneities generated by a critically focused cw laser beam. We find that the Stokes and anti-Stokes bands are extensively deformed due to large asymmetric broadenings which develop on the side of the low-frequency shifts. The broadenings are thus attributed to temperature gradients and are shown to be important in determining temperature distributions.
Temperature dependence of the mobility of two-dimensional hole systems in modulation-doped GaAs-(AlGa)As
Authors: Störmer H. L. , Gossard A. C. , Wiegmann W. , Blondel R. , Baldwin K.
Published: February 2003

The temperature dependence of the mobility of two-dimensional hole systems at modulation-doped GaAs-(AlGa)As heterojunctions is determined. Its shape follows closely the equivalent curve for high-purity p-type bulk GaAs. Low-temperature mobilities beyond 4×104 cm2/Vs are found for areal hole densities of 5×1011 cm−2. The equivalent scattering times reach those of the best modulation-doped electron systems. In the temperature range where acoustic mode scattering prevails a T−3/4 dependence was observed. Studies under light illumination could not detect any persistent photoconductive effect in two-dimensional holes.
Silicon photodetector integrated on a lithium tantalate substrate
Authors: Reedy R. E. , Lee S. H.
Published: February 2003

We report the fabrication of metal-oxide-semiconductor field-effect transistors (MOSFET’s) in laser recrystallized silicon films on a lithium tantalate substrate with an intervening silicon dioxide layer. Deposited polycrystalline silicon films were irradiated with a scanning focused argon ion laser beam which caused melting and subsequent crystallization of the silicon film into crystallites suitable for MOSFET fabrication. Melting and recrystallization of the silicon film without damaging the substrate were accomplished by irradiation with 0.3–0.4 W of argon ion laser power focused to a 50-μm-diam spot. Transistor channel mobility was measured to be 50 cm2/Vs. When operated as integrated photodetectors, a responsivity of approximately 0.5 A/W was measured. Theoretical operation of these MOSFET’s as integrated photodetectors is derived and compared to observed operation.
Submicron, vacuum ultraviolet contact lithography with an F2 excimer laser
Authors: White J. C. , Craighead H. G. , Howard R. E. , Jackel L. D. , Behringer R. E. , Epworth R. W. , Henderson D. , Sweeney J. E.
Published: February 2003

An F2 excimer laser at 157 nm has been used for the first time as an exposure source for high resolution photolithography. At this short wavelength, conventional glass and quartz mask substrates are opaque, and therefore alkaline-earth halides and sapphire were used as mask substrates. The masks were patterned by electron beam lithography, and mask features as narrow as 150 nm have been replicated and represent the smallest features yet produced by contact photolithography.
Miniature SQUID susceptometer
Authors: Ketchen M. B. , Kopley T. , Ling H.
Published: February 2003

We present a new dc superconducting quantum interference device (SQUID) configured as a susceptometer for the study of the magnetic properties of small (<10 μm) particles and thin-film samples. The SQUID consists of two series pick-up loops wound in opposite sense over a hole in the groundplane and connected to remotely located tunnel junctions by low inductance transmission lines. An integrated field coil with provision for balance allows application of a magnetic field of 0–30 G to a sample positioned in either pick-up loop. For an applied field of 5 G the device having an intrinsic energy sensitivity of ∼25 h is able to resolve the superconducting transition of a 5-μm tin particle with a signal-to-noise ratio of ∼106.
Temperature dependence of threshold current of injection lasers for short pulse excitation
Authors: Dutta N. K. , Olsson N. A. , Heritage J. P. , Liu P. L.
Published: February 2003

We report measurements of the temperature dependence of the threshold current of GaAs, 1.3-μm InGaAsP, and 1.5-μm InGaAsP double heterostructure lasers using short electrical pulses. T0∼200 K is observed for all the lasers. These high T0 values show that the carrier density at threshold does not increase rapidly with increasing temperature in any of the lasers studied and thus the observed low cw T0 of InGaAsP lasers is primarily due to a decrease of the carrier lifetime at threshold with increasing temperature.
Low threshold GaInAsP/InP buried-heterostructure lasers with a chemically etched and mass-transported mirror
Authors: Liau Z. L. , Walpole J. N. , Tsang D. Z.
Published: February 2003

The mass-transport technique has been used to improve chemically etched mirrors on GaInAsP/InP double heterostructure wafers. Vertical and flat mirror facets have been obtained. Buried-heterostructure lasers fabricated with one such mirror and the other mirror cleaved show high device yield with threshold currents as low as 6 mA and differential quantum efficiency as high as 33%.
Minority-carrier diffusion lengths in GaP/GaAsxP1−x strained-layer superlattices
Authors: Gourley P. L. , Biefeld R. M. , Zipperian T. E. , Wiczer J. J.
Published: February 2003

We have made the first measurements of the minority-carrier diffusion lengths L∥ and L⊥ respectively in both n- and p- type GaP/GaAsxP1−x 〈100〉 strained-layer superlattices (SLS’s) in directions parallel and perpendicular to the interfaces. Using room-temperature optical techniques, we find that L⊥≊0.1 μm, which is more than an order of magnitude smaller than L∥≊1.5 μm. The latter is comparable to that measured in the bulk materials which comprise the SLS layers, while the former demonstrates the existence of large potential barriers in both the conduction and valence bands.
Disilane: A new silicon doping source in metalorganic chemical vapor deposition of GaAs
Authors: Kuech T. F. , Meyerson B. S. , Veuhoff E.
Published: February 2003

Disilane (Si2H6) is presented as a new silicon doping source in the metalorganic chemical vapor deposition of GaAs together with comparison results obtained using the conventional silane (SiH4) doping source. The doping characteristics of disilane were studied over a wide range of growth conditions: temperature, gas phase stoichiometry, and disilane concentration in the growth ambient. Silicon incorporation by means of disilane pyrolysis showed no temperature dependence, in sharp contrast to the strong temperature activated dependence found when employing silane. The decomposition reaction of disilane proved to be very efficient, reducing the amount of dopant gas required by about two orders of magnitude at the lower growth temperatures. Electrical measurements on disilane-doped GaAs yield the same high mobilities as obtained in silane-doped GaAs films, indicative of low compensation.
New mode of plasma deposition in a capacitively coupled reactor
Authors: Hamasaki T. , Ueda M. , Chayahara A. , Hirose M. , Osaka Y.
Published: February 2003

A new technique of radio frequency plasma-enhanced chemical vapor deposition is developed to achieve extremely high growth rates exceeding 40 Å/s. The two disk electrodes are surrounded by a stainless-steel mesh at ground potential, and an external variable reactance is connected between the substrate electrode and the ground. When the resonance condition in the circuit composed of the variable reactance and the substrate sheath capacitance is satisfied, a very high deposition rate is obtained as a result of dramatic change in the potential distribution between the two electrodes.
Modulation-doped field-effect transistor based on a two-dimensional hole gas
Authors: Störmer H. L. , Baldwin K. , Gossard A. C. , Wiegmann W.
Published: February 2003

We report the successful operation of the first p-type, modulation-doped field-effect transistor ( p-MODFET). The channel consists of a two-dimensional hole gas at a GaAs/(AlGa)As heterostructure interface. With a gate length of 2 μm and a source-drain distance of 7 μm we achieve transconductances of 28 mS/mm at 77 K and 44 mS/mm at 4.2 K. This work represents the first demonstration of a p-type transistor that is the complement of the conventional n-MODFET.
High mobility electron gas in selectively doped n:AlGaAs/GaAs heterojunctions
Authors: Heiblum M. , Mendez E. E. , Stern Frank
Published: February 2003

Selectively doped n:AlGaAs/GaAs heterojunctions have been grown by molecular beam epitaxy, employing a slow growth technique, at a substrate temperature of 600 °C. The effect of the undoped AlGaAs spacer thickness on carrier density and Hall mobility was investigated. Mobilities as high as 9200, 200 000, and 1 060 000 cm2/Vs at 300,77, and 4.2 K, respectively, were measured in the dark for a spacer thickness of ∼180 Å and an areal carrier density of ∼2.2×1011 cm−2. Surprisingly, samples with spacer thicknesses of 80 Å had 4-K mobilities of ∼800 000 cm2/Vs, higher than expected theoretically from the structural parameters.
Chemical reactions at the noble and near-noble metal/InP interfaces: Comparison to Si and GaAs
Authors: Kendelewicz T. , Petro W. G. , Lindau I. , Spicer W. E.
Published: February 2003

The room-temperature chemical reactions of noble (Cu, Ag, Au) and near-noble transition (Ni, Pd) metals with the vacuum cleaved InP (110) surface have been studied with surface sensitive photoemission spectroscopies. It has been shown that the chemical reactions at these interfaces are closely similar to the reactions taking place on silicon substrates. In particular all metals that react strongly with Si to produce silicides (Cu, Ni, Pd) also form stable phosphides. This reaction is accompanied by phase segregation of metallic In. In addition, for Au (intermixing without a stable compound with P) and Ag (very weak reaction with substrate; growth of metallic Ag islands) the reactions with both InP and Si are qualitatively identical. It has been found that for GaAs the reactions with noble and near-noble metals, though weaker than for InP, follow the same pattern.