Showing papers on "Van der Pauw method published in 1991"

Thin films of CuInSe2 produced by rf sputtering with intentional oxygen doping

Abstract: Structural, electrical, and optical properties of CuInSe2 thin films produced by rf sputtering from a stoichiometric target in an Ar/O2 atmosphere are presented. The growth rate decreases rapidly with increasing constituent gas ratio [O2]/([Ar]+[O2]). From x‐ray diffraction, Auger electron spectroscopy, and x‐ray photoelectron spectroscopy, it can be seen that CuInSe2 and In2O3 are mixed in the thin films for [O2]/([Ar]+[O2])≳3%. SeO2, CuO, and In2O3 coexist together at the surface of these thin films. Hot probe analyses indicate that these thin films show n‐type conduction. The Van der Pauw measurements and the optical transmittance measurements show that the resistivity decreases and the band gap increases with an increase in the [O2]/([Ar]+[O2]) ratio.

On-wafer Hall-effect measurement system

Abstract: A non-destructive measurement system for producing whole wafer maps of sheet Hall concentration and Hall mobility in a GaAs wafer. The wafer need only have van der Pauw patterns available for the wafer measurements to be made. The measurement system includes an automatic test prober apparatus modified to incorporate a powerful permanent magnet providing a magnetic field to produce a Hall effect in the GaAs wafer. A parametric measurement system coupled through test probes to the van der Pauw patterns is programmed to measure sheet resistivity, Hall voltage and magnetic field strength, from which are derived values of sheet Hall concentration and mobility that are stored and mapped.

Electrical characterization Of SiGe thin films

Abstract: An apparatus for measuring electrical resistivity and Hall coefficient on both thin films and bulk material over a temperature range of 300K to 1300K has been built. A unique alumina fixture, with four molybdenum probes, allows arbitrarily shaped samples, up to 2.5 cm diameter, to be measured using van der Pauw's method. The system is fully automated and is constructed with commercially available components. Measurements of the electrical properties of doped and undoped Si-Ge thin films, grown by liquid phase epitaxy reported here, are to illustrate the capabilities of the apparatus.

Precipitation of arsenic diffused into silicon from a TiSi2 source

Abstract: The diffusion into a p‐type Si substrate of arsenic ions implanted into TiSi2 layers has been investigated for several thermal diffusion treatments in the 900–1100 °C temperature range. The drive‐in was performed using either a rapid thermal annealing system or a traditional furnace. Shallow (20–80‐nm depth) junctions were obtained with a high (1019–1020/cm3) dopant concentration at the silicide‐silicon interface. The amount of diffused arsenic atoms measured by Rutherford backscattering spectrometry increases linearly with the square root of the annealing time. A similar relation was found for the amount of electrically active arsenic, as measured by Van der Pauw structure in combination with anodic oxidation. The two quantities differ and the inactive dopants precipitate in the diffused layer as seen by transmission electron microscopy. This behavior might be associated to the high tensile stress induced by the silicide layer on the surface silicon region and to its influence on the solid solubility and...

Magnetron sputtered TiAlON composite thin films. II. Optical and electrical properties

Abstract: The optical and electrical properties of well characterized composite TiAlON thin films are presented. The samples display a low reflectance in the visible–near‐UV spectral range (below 16%) and high absorption coefficients (1–4×105 cm−1). Standard deposition conditions, defined with respect to the desired functional properties as decorative coatings, yield the darkest shades with flat reflectance spectra (between 10% and 12%). Spectroscopic ellipsometry studies show that these features are intrinsically related to the two‐phase structure. Differences among the samples result from the porosity level inherent to columnar microstructures. The generalized Maxwell Garnett theory is used to estimate the level of porosity in standard TiAlON. A void fraction of 0.15 is calculated, well correlated with the available microstructural observations. The electrical resistivities of 2 μm thick TiAlON films are determined by the van der Pauw method. At room temperature, values between 10−3 and 10−2 Ω m are measured for ...

The determination of the deformation potential constant of the conduction band in InSb by the electron mobility in the intrinsic range

Abstract: The electron Hall mobility in InSb has been measured at 200~430 K by van der Pauw's method. The experimental data were compared with theoretical values calculated by an iteration technique with a variable parameter |El|. In the calculations, the temperature dependence of m* was estimated from the experimental data of Eg(T) and m*(0) on the basis of Ravich's theory, and the value of κs was taken to be 16.8 instead of κs~17.5. The comparison between the theoretical and experimental values of µH led to the value of |El|=33 eV, which is more than two times larger than that obtained in a previous work.

Percolative reconciliation between resistive and magnetic measurements of the transition temperature in HTS thin films

Abstract: Several Bi-Sr-Ca-Cu-O thin films have been produced ex situ by sequential thermal evaporation. Characterizing the transition temperatures Tc of these films, a constant discrepancy between resistive and inductive measurements is observed. The resistive van der Pauw technique indicates Tc (onset) typically above 90 K and Tc (zero) at around 78 K. However, the Tc (onset) for these same films is not seen by an inductive measurement, in which the film surface is in physical contact with a flat spiral coil, inducing changes in the coil inductance during the superconductivity transition. Conversely, the inductive transition starts around 5 K above the resistively obtained Tc (zero). Percolation theory is employed in an attempt to explain this discrepancy and to establish generally how Tc (zero) can be found from the resulting curve in the inductive measurement technique.

Electromigration characteristics of vias in Ti:W/Al-Cu(2 wt.%) multilayered metallization

Abstract: The electromigration (EM) performance and failure mechanisms for 1.2- mu m vias fabricated in a passivated Ti:W/Al-Cu(2 wt.%) metallization were investigated. Single van der Pauw via structures were stressed at 175 degrees C and 200 degrees C and at accelerated current densities. The via resistance was monitored independently of the metal feed lines and a difference in activation energy, failure mode, and mean time to fail was observed depending on the direction of current flow. When electrons flowed into the via, the via sustained a 20% increase in resistance before failing catastrophically. Conversely, when electrons flowed out of the via, a monotonic increase in resistance was observed, and yet the via remained intact. Concerns of poor aluminum step coverage in the vias were addressed. Reliability comparisons were made between vias and flat metal stripes. >

Effect of laser irradiation on structural, electrical, and optical properties of p-mercury cadmium telluride

Abstract: Single crystals of p‐Hc1−xCdxTe (x=0.16) were grown by the Bridgeman technique. The bulk single crystals were irradiated with laser pulse of various energy densities. A pulsed laser (Nd:YAG) capable of producing 10‐ns pulses of 0.53 μm wavelength (frequency doubled) with varying energy densities (2–50 mJ/cm2) was employed. dc conductivity and Hall coefficient measurements were made on the single crystal using the Van der Pauw technique in the temperature range 77–300 K for both as‐grown and laser‐irradiated samples. Also the x‐ray diffraction pattern and transmission measurements of the samples were taken at room temperature. Electrical studies shows that the p‐mercury cadmium telluride after the laser irradiation becomes n type and optical results show that the free‐carrier concentration after laser irradiation increases sharply so that there is negligibly small transmission. The x‐ray studies show that single crystal p‐type samples after laser irradiation undergo structural changes as well, introducing ...

Effect of laser annealing on electrical and optical properties of n‐mercury cadmium telluride

Abstract: Single crystals of n‐Hg1−xCdxTe (x=0.18) were grown by the Bridgman technique. The bulk single crystals were irradiated with laser pulses of various energy densities. A pulsed laser (Nd:YAG) capable of producing 10‐ns pulses of 0.53‐μm wavelength (frequency doubled) with varying energy densities (2–50 mJ/cm2) was employed. dc conductivity and Hall coefficient measurements were made on the single crystal using the van der Pauw technique in the temperature range 77–300 K, for both as‐grown and laser‐irradiated samples. Also, transmission measurements of the samples were taken at room temperature. Both electrical and optical studies showed that laser irradiation introduces additional defects in mercury cadmium telluride (MCT), and its quality deteriorates instead of improving as observed in many other semiconductor materials. We found that laser irradiation increases free‐carrier concentration and decreases the band gap of MCT.

Structural, elastic and transport properties of Ag/Al multilayer thin films prepared by ion-beam sputtering

Abstract: Multilayers of Ag/Al with composition modulation wavelengths λ between 13.5 and 210 A were deposited onto silicon substrates using ion-beam sputtering. X-ray diffraction scans showed well defined small angle peaks and satellite peaks at high angles indicating coherent multilayers. The average lattice parameter showed a 1.1% reduction with decreasing modulation wavelengths from 90 to 25 A. Brillouin-scattering measurements showed a moderate 5% enhancement of surface velocity (elastic constant) with decreasing wavelengths. This elastic hardening and interplanar structural contraction may be partially attributed to the observed formation of Ag2Al at the multilayer interfaces. Although deposited only 10° from a normal incidence, the electrical resistivities, measured between 77 and 300 K in a van der Pauw configuration, showed a temperature independent in-plane anisotropy of up to 90% and the room temperature resistivity was an order of magnitude greater than expected from the bulk average. The temperature coefficient of resistivity showed a “U” shaped dependence with λ and the lower up turn occurred at λ ≈ 50 A.

Annealing of damage-induced deep levels in MeV Si-implanted GaAs

Abstract: Structural and electrical characteristics of MeV Si ion-implanted and thermally-annealed GaAs samples are reported. The annealing behavior of strain depth profiles is correlated with the annealing behavior of implant-induced defects. The depth profiles of carrier concentration and mobility were obtained by van der Pauw Hall measurements and successive layer removal by chemical etching. The concentration depth profiles suggest defect-assisted diffusion of the dopants and the mobility profile shows a broad minimum due to the residual damage. Deep level transient spectroscopy (DLTS) measurements revealed two electron traps at Ec − 0.59 eV and at Ec − 0.83 eV in the implanted region. An almost complete removal of both traps was observed after a rapid thermal annealing (RTA) at 950 °C and an additional furnace annealing at 750 ° C. It is suggested that AsGa antisite defects are involved in both traps. The I − V − T measurements show a large leakage current in the diodes made in the high-trap-density region of an RTA-annealed sample. This large leakage current is shown to be caused by the trap-assisted tunneling process in the Schottky junction.

InP Layers Grown by Molecular Beam Epitaxy at Low Substrate Temperature

Abstract: InP layers were grown on semi-insulating InP wafer by molecular beam epitaxy (MBE) at low substrate temperatures (<200° C), using solid phosphorus source. We use x-ray diffraction, double crystal x-ray rocking curve, Auger electron spectroscopy, and temperature-dependent Van der Pauw and Hall effect measurements to characterize the as-grown and annealed InP layers. It is found that the InP layer is in poly-crystal state with excess P over 7 at%. The layers became single crystal after annealing above 400°C. The resistivity of the InP layer decreased from 60 Ωcm for an as-grown sample to 0.82 Ωcm after 400°C RTA annealing. The different role of excess P as compared to the role played by excess As in LT-GaAs is discussed based on the P properties.

InSb/CdTe heterostructures grown by MBE

Abstract: InSb/CdTe heterostructures were grown by MBE, including a 10 layer “superlattice”. The structures were characterized by X-ray diffraction, van der Pauw measurements, and SNMS depth profiling. The interfaces widen because of interdiffusion and through the formation of an interface compound from the reaction of Te with the InSb surface. The interface compound is identified as strained InTe(II). The interfaces are still too wide for practical devices. Thermochemical analysis indicates that the reaction can be suppressed by applying a Cd overpressure. The diffusion of In and Sb in CdTe is very fast and will necessitate a MEE growth scheme at lower temperatures.

Structural and electrical properties of Si layers implanted with various Ge ion doses

Abstract: Si layers amorphized with various Ge+ doses at 100 keV have been evaluated using Rutherford backscattering spectrometry and the van der Pauw technique. The recovery of crystallinity for the samples implanted with a critical dose (≈5 × 1014/cm2), required to amorphize silicon at 100 keV, is achieved by an annealing treatment of 550°C for 60 min. The rates of regrowth for the (1OO)-oriented samples annealed at 550°C are also discussed. The electrical properties of the implanted layer are not altered by annealing at 550°C for 60 min.

Liquid Phase Epitaxy Growth and Properties of GaInAsSb/AlGaAsSb/GaSb Heterostructures

Abstract: The GaInAsSb/AlGaAsSb/GaSb heterostructures were grown by the liquid phase epitaxy (LPE) technique. The materials were characterized by means of optical microscopy, electroprobe microanalysis (EPMA), double-crystal X-ray diffraction, capacitance-voltage (C-V) and Van der Pauw measurments, infrared absorption spectra, photoluminescence and laser Raman scattering. The results show that the materials have fine surface morphology, low lattice mismatch and good homogeneity. Room-temperature light-emitting diodes with an emission wavelength of 2.2-mu-m were obtained by using the GaInAsSb/AlGaAsSb DH structures.

Amorphization and recrystallization of epitaxial ReSi2 films grown on Si(100)

Abstract: The effects of implantation damage and the chemical species of the implant on structural and electrical properties of epitaxial ReSi2 films on Si(100) implanted with Si-28 or Ar-40 ions, at doses ranging from 10 to the 13th/sq cm to 10 to the 15th/sq cm, were investigated using the backscattering spectrometry, XRD, and the van der Pauw techniques. Results showed that ion implantation produces damage in the film, which increases monotonically with dose; the resistivity of the film decreases monotonically with dose.

Electrical activation process of erbium implanted in silicon and SIMOX

Abstract: The electrical activation mechanism of erbium implanted in silicon and SIMOX (separation by implanted oxygen) following different annealing processes is studied by using the Van der Pauw technique in combination with photoluminescence and Rutherford backscattering angular scanning measurements. The results show that the Sactivation of the erbium is related to the lattice configuration. In the case of conventional furnace annealing, the activation corresponds to an occupation of erbium on substitutional lattice sites, but in the case of rapid thermal annealing, it corresponds to the occupancy of both interstitial with a tetrahedral (Td) symmetry and substitutional lattice sites. The transfer of interstitial erbium to substitutional sites corresponds to an electrical deactivation process due to partial compensation of the n-type and p-type carriers produced by the two different electrically active erbium sites.

Concentration profiles and electrical characterization of high energy phosphorus implants in 〈100〉 silicon

Abstract: Phosphorus ions in the energy range 0.25–1 MeV and in the dose range (2 × 10 13 )–(1 × 10 15 ) cm −2 were implanted on Si 〈100〉single crystals at a tilt angle of either 3° or at 7° with respect to the normal. For comparison some implants were performed on samples with a surface amorphous layer 2 μm thick. Carrier concentration and mobility profiles of the implanted species were carried out by Van der Pauw measurements and by spreading resistance profilometry analyses. The presence of channelling tails due to the feeding-in effect was evidenced and studied as a function of dose and implantation angle. These data are discussed and compared with Monte Carlo calculations using the Marlowe code.

Carbon Doping of GaAs by OMVPE Using CC14: A Comparison of Gallium and Arsenic Precursors

Abstract: The carbon doping properties of GaAs with carbon tetrachloride as the dopant source were examined using trimethylgallium (TMGa) or triethylgallium (TEGa) as the gallium precursors and arsine or tertiarybutylarsine (TBAs) as the arsenic precursors. Secondary ion mass spectrometry (SIMS) and Hall measurements (van der Pauw method) were used to characterize the epitaxial GaAs:C layers. Very high C-doping concentrations (∼1020 cm−3) could be obtained with either TMGa and TEGa. The use of TBAs instead of AsH3 led to a significant reduction in carbon incorporation, by approximately a factor of 5-10 per mole of As precursor, over the temperature range examined (520°C - 700°C). Hydrogen at significant concentrations (0.5 - 6 x 1019 cm−3) was detected by SIMS in GaAs:C layers grown at ≤550°C utilizing all four combinations of Ga/As precursors and suggested the presence of electrically inactive C-H complexes. A post-growth anneal under helium at 550°C for 60s of these samples resulted in a 50-100% increase in hole concentration by driving out the hydrogen.

A micro-uniformity test structure

Abstract: The uniformity of ion implantation across a chip is becoming more important as the density of devices on a chip increases and the matching tolerance of device parameters across a chip decreases and becomes more critical. In order to investigate ion-implant micro-uniformity, a special van der Pauw mask was designed with 400 structures per square centimeter. This mask has been used with a polysilicon-on-oxide test structure to investigate chip micro-uniformity. Both medium- and high-current implanters have been studied using this dense van der Pauw pattern. Contour maps, 3D maps and histograms are used to display the variation of dose across a chip area. Results are also presented for micro-nonuniformity patterns deliberately introduced on a wafer. Several optical techniques are also presented to map closely spaced stripes across the wafer.