Showing papers on "Van der Pauw method published in 1990"
TL;DR: In this paper, the GaAs buffer layer effects on residual stress and defect density in InP/Si have been clarified using low-pressure organometallic vapor phase epitaxy.
Abstract: Heteroepitaxy of a highly mismatched system (∼8%), InP/Si, has been studied using low‐pressure organometallic vapor phase epitaxy. GaAs buffer layer effects on residual stress and defect density in InP/Si have been clarified. Using a 1‐μm‐thick GaAs buffer layer, residual stress in the InP layer has been reduced to as low as 2×108 dyn/cm2 compared to ∼4×108 dyn/cm2 for InP directly grown on Si. Moreover, the GaAs buffer layer has also been confirmed to be effective for improving InP/Si quality by evaluation of etch‐pit density, x‐ray diffraction measurement, and cross‐sectional transmission electron microscopy. Electrical properties of InP layers on GaAs/Si were evaluated with the van der Pauw and deep level transient spectroscopy (DLTS) methods. The heteroepitaxial layer’s own electron trap has also been observed by DLTS measurements. For an InP/GaAs/Si structure, InP growth temperature effect on surface morphology and etch‐pit density is also shown. High quality InP films with an etch‐pit density of 8×1...
74 citations
TL;DR: In this article, the anisotropic properties of YBa2Cu4O8 have been investigated using the Montgomery formalism for anisotropies using single crystal platelets by optical and electron transport measurements.
Abstract: The anisotropy within the a-b plane of YBa2Cu4O8 has been studied on single crystal platelets by optical and electron transport measurements. The optical investigations include polarized reflectivity measurements at room temperature for photon energies between 0.5 and 4 eV and a direct measurement of the ratio of the reflectivity coefficients r b r a . The anisotropy of the electrical resistivity has been determined from AC van der Pauw measurements using the Montgomery formalism for anisotropic materials. The optical reflectivity spectra are dominated by Drude-like free electron contributions with plasmon energies of 2.8 eV and 1.67 eV for the electrical field vector along the b- and a-axis, respectively. The electrical resistivity displays an anisotropy of a factor of about 3. The superconducting transition temperature (midpoint of the resistivity drop) is 76 K. Contrary to YBa2Cu3O7, clear deviations from linear temperature dependences of the resistivity are observed in the normal state of YBa2Cu4O8. An extrapolation of the linear (normal) part gives zero resistance at 36 ± 2 K and not 0 K. The observed anisotropies are compared with results of a tight binding calculation.
37 citations
TL;DR: In this paper, the thermal stability of polycide structures with narrow lines was investigated as a function of the dopants introduced into the polysilicon (i.e., boron or arsenic) in the temperature range from 700 to 950 degrees.
Abstract: The thermal stability of TiSi2/poly‐Si structures with narrow lines has been studied as a function of the dopants introduced into the poly‐Si (i.e. boron or arsenic) in the temperature range from 700 °C to 950 °C. The silicide layer was formed by rapid thermal processing (RTP) in nitrogen via a solid–solid reaction between titanium and poly‐Si. The integrity, upon heat treatment, of the TiSi2 film on large areas was investigated by Rutherford backscattering spectroscopy (RBS) analysis, plan‐view scanning electron microscopy (SEM), and cross‐sectional SEM studies. Electrical information about the thermal stability of the bilayer was obtained from sheet resistance measurements on Van der Pauw structures in combination with linewidth measurements of bridge resistors with a nominal width between 0.8 and 1.5 μm. To provide for statistical variation about one hundred measurements were collected for each linewidth and temperature setting. The results clearly show that the thermal stability of the bilayer is a function of the amount and type of dopants in the polysilicon, favoring the use of high levels of arsenic. Moreover, the thermal stability was observed to be affected by the linewidth, since at the temperature for onset of degradation (above 900 °C), narrow lines were found to disintegrate at a much higher rate than wider ones. Cross‐sectional SEM and TEM micrographs of the polycide lines clearly reveal the TiSi2/poly‐Si interface to suffer from bowing. The effect was observed to be more pronounced on narrow undoped and boron‐doped polycide lines. Both the narrow line disintegration and the bowing effect of polycide structures can have important implications for submicron very large scale integrated (VLSI) technologies.
24 citations
TL;DR: In this article, the authors evaluated the depth uniformity of electrical properties of semi-insulating GaAs irradiated with thermal neutrons of 1.5×1018 cm−2 by the van der Pauw method combined with iterative etching of the surface.
Abstract: Depth uniformity of electrical properties has been evaluated for neutron‐transmutation‐doped (NTD), semi‐insulating GaAs irradiated with thermal neutrons of 1.5×1018 cm−2 by the van der Pauw method combined with iterative etching of the surface. In NTD‐GaAs wafers (thickness ∼410 μm) annealed for 30 min at 700 °C, the depth profiles of the resistivity, the carrier concentration, and the Hall mobility show constant values of 1×10−2 Ω cm, 2.0×1017 cm−3, and 3100 cm2/V s, respectively, within an experimental error of 5%. In an annealing process, the redistribution and/or the segregation of NTD impurities is not observed. We also discuss the limitations of low‐level NTD in semi‐insulating GaAs. It is suggested that the activation of the NTD‐impurities below ∼1×1016 cm−3 is mainly restricted by the presence of the midgap electron trap (EL2).
16 citations
TL;DR: In this article, the horizontal Bridgman (HB) technique has been used to grow 2-inch diameter Si-doped GaAs crystals with a carrier concentration of 1.7-2.0 times higher than that of non-facet areas.
14 citations
TL;DR: In this paper, the well layer thickness and In composition were analyzed by ion channeling and particle-induced x-ray emission as a function of growth temperature, and the observed differences in film quality can be explained by the influence of substrate temperature and As4 flux on the cation surface mobility during growth of the InGaAs layer.
Abstract: Strained GaAs/InGaAs/AlGaAs quantum well structures have been grown by molecular beam epitaxy at substrate temperatures from 375 to 510 °C. The well layer thickness and In composition are analyzed by ion channeling and particle‐induced x‐ray emission as a function of growth temperature. Test structures for modulation‐doped field‐effect transistors grown at 375 and 510 °C under two different As4 overpressures were also characterized by Van der Pauw measurements and low‐temperature photoluminescence. The observed differences in film quality can be explained by the influence of substrate temperature and As4 flux on the cation surface mobility during growth of the InGaAs layer.
13 citations
TL;DR: Tiong et al. as mentioned in this paper showed that the regrowth stages and regrowth rates of disordered gallium arsenide (GaAs) in the annealing process depend on the excitation wavelength and anneal temperature, and the damaged layer regrows epitaxially toward the surface.
Abstract: The structures of microcrystalline or amorphous gallium arsenide (GaAs) introduced by 120‐keV Si+‐ or P+‐ion implantation with a dose of 1×1016 atoms/cm2 and the subsequent regrowth properties annealed by rapid thermal annealing in the range from 300 to 900 °C have been investigated by Raman scattering (RS) and by the van der Pauw measurement (sheet carrier concentration and sheet resistivity) [Phillips Res. Rep. 13, (1958)]. Raman spectra of the LO‐phonon mode observed for 514.5‐ and 457.9‐nm excitation of an Ar+ laser have been analyzed on the basis of a spatial correlation model [H. Richter et al., Solid State Commun. 39, 625 (1981); K. K. Tiong et al., Appl. Phys. Lett. 44, 122 (1984)]. The results show that the regrowth stages and the regrowth rates of the disordered GaAs in the annealing process depend on the excitation wavelength and annealing temperature, and the damaged layer regrows epitaxially toward the surface. Sheet carrier concentration was observed to increase steeply, and sheet resistivit...
13 citations
NEC1
TL;DR: In this paper, an X-ray exposure mask was evaluated using electrical test structures, including four-terminal bridges and van der Pauw resistivity and fourterminal bridge resistance, and it was confirmed that electrical measurement has very high accuracy and reproducibility.
Abstract: An X-ray exposure mask was evaluated using electrical test structures. Linewidth was calculated from van der Pauw sheet resistivity and four-terminal bridge resistance. The four-terminal bridge gave a high resolution of 0.002 mu for 0.6- mu m patterns. It was confirmed that the electrical measurement has very high accuracy and reproducibility. A misalignment vector map was demonstrated by a pair o four-terminal bridges. The van der Pauw resistor was also applied for reducing batting error in electron-beam lithography. >
7 citations
TL;DR: The interlayer van der Pauw (VDP) resistor alignment bridge as discussed by the authors combines the sheet resistor and registration-sensitive bridge into one unified structure, which uses minimum area and pad count and provides orthogonal registration measurements.
Abstract: The interlayer van der Pauw (VDP) resistor alignment bridge combines the sheet resistor and registration-sensitive bridge into one unified structure. As a result of symmetry, it does not require the width corrections resulting from image exposure and etch variations typical of linear resistor structures. It uses minimum area and pad count and provides orthogonal registration measurements. Bridges designed for 1.5- mu m feature size with body dimensions of 18 and 21 mu m and a tap length to width ratio of 0.5 show a sensitivity of 34-38 mV/ mu m at 10 mA. Registration errors of 0.2 mu m have been measured with an error of less than 10%. A good statistical correlation has been obtained between drawn and measured registration offsets. The correlation between the VDP bridge and the optical vernier is within +or-2% using a vernier spacing of 0.125 mu m. These results clearly indicate that the VDP bridge has the potential to provide accurate measurements of photo mask registration with the precision required for very large scale integration (VLSI) processing. The application of the VDP resistor bridge for interlayer registration using standard production procedures is described. Measurement precision and accuracy are discussed along with some fundamental bridge-design considerations. >
6 citations
TL;DR: In this article, the authors present a brief and simplified summary of the transport processes involved in vapor-phase epitaxy (VPE) and the differences and similarities between hydride and chloride VPE.
Abstract: Publisher Summary This chapter presents a study on high purity indium phosphide (InP) grown by hydride vapor phase epitaxy. The chapter presents a brief and simplified summary of the transport processes involved in vapor-phase epitaxy (VPE) and the differences and similarities between hydride and chloride VPE. In both hydride and chloride VPE, pure metals are transported by chlorine from HCl. The reactor used for the growth of high purity InP should be as simple as possible and free of sources of unwanted impurities. The reactor used in the study described in the chapter was originally designed for the growth of doped binary, ternary, and quaternary multilayered structures. Substrate surface orientation and preparation are very important for epitaxial layer quality in hydride (H)-VPE. Hall-effect measurements at room temperature and liquid nitrogen temperature have become the accepted method to determine carrier concentration and mobility of high purity samples. Hall-effect measurements were made by the Van der Pauw technique. Geometry is important for Hall measurements. The chapter discusses photothermal ionization spectroscopy, magneto-photoiuminescence measurement, and constant capacitance-deep level transient spectroscopy.
4 citations
23 Feb 1990
TL;DR: In this article, the carrier activation and deep level crystal defects in pulsed excimer laser (A = 308 nm) anealed samples of GaAs implanted with Si and Se to a dose ranging from 2.2 x 1012 to 6.0 x 10" cm'.
Abstract: In this paper, we report on the carrier activation and deep level crystal defects in pulsed excimer laser (A = 308 nm) anealed samples of GaAs implanted with Si and Se to a dose ranging from 2.2 x 1012 to 6.0 x 10" cm'. The residual defects in the pulsed-laser annealed GaAs have been investigated by means of photo-induced current transient spectroscopy (PITS). The electron concentration and carrier mobility were studied by Hall effect and Van der Pauw measurements. Although the implanted layer recrystallization was good and the sheet carrier concentration was high, the electron mobility was low. The correlation between deep traps, the carrier concentration, the electron mobility, and laser light intensity is presented.
TL;DR: In this paper, the effects of rapid thermal annealing (RTA) on the electrical activity of various implanted dopants (Be, Mg, Zn, and Hg) in semi-insulating GaAs have been studied by Van der Pauw Hall measurements and Polaron profiling.
Abstract: The effects of rapid thermal annealing (RTA) on the electrical activity of various implanted dopants (Be, Mg, Zn, and Hg) in semi‐insulating GaAs have been studied by Van der Pauw Hall measurements and Polaron profiling. The relationship between the observed variation in the electrical activation energies of these acceptors and their local electronegativity has been investigated to envisage the possible microscopic mechanism of the activation of the dopants in GaAs.
Patent•
28 Feb 1990
TL;DR: In this paper, the effect of a surface depletion layer is removed from a sheet carrier concentration calculated by Hall measurement, and an accurate impurity activation rate from which the effect is removed is found.
Abstract: PURPOSE:To find an accurate impurity activation rate even in the case of a low dose by a method wherein the effect of a surface depletion layer is removed from a sheet carrier concentration calculated by Hall measurement. CONSTITUTION:A plurality of pieces of semiconductor samples, whose impurity activation rates ought to become identical with one another and whose doses Nd only of impurity are different from one another, are prepared. Then, a sheet carrier concentration Ns is calculated by Hall measurement based on a van der Pauw's method as to each sample. Moreover, an impurity activation rate (n) to correspond to each dose Nd is found by Formula (I) from a plurality of groups of (Nd and Ns/Nd ). Thereby, an accurate impurity activation rate, from which the effect of a surface depletion layer is removed, is found.
TL;DR: In this article, a uniformn-layer by multiple29Si+ implantation on LEC grown semi-insulating GaAs substrate and its characterisation by differential Hall measurement at room temperature is reported.
Abstract: Formation of a uniformn-layer by multiple29Si+ implantation on LEC grown semi-insulating GaAs 〈100〉 substrate and its characterisation by differential Hall measurement at room temperature is reported. The implantation energies are 60, 160 and 260 keV with corresponding doses of 1 × 1012, 2·55 × 1012 and 3 × 1012 cm−2. Asimplanted, uncapped substrates were furnace-annealed with face-to-face configuration in an N2 ambient at 850°C with arsenic overpressure. After annealing, the samples were subjected to Hall measurements using Van der Pauw configuration. Experimental and theoretical (LSS) profiles are compared. Electrical activation of the dopant atoms was found to range from 65–90% with average mobility values lying between 2000–2300 cm2 V−1 s−1. Uniform concentration of then-layer ∼ 1017 cm−3 up to a depth of 0·3 µm has been achieved. These layers are used for the fabrication of power MESFETs.
TL;DR: In this article, a two-source thermal evaporation method was used to prepare polycrystalline InSb thin films and the electrical mobility value of the thin film was measured by the Van der Pauw's method.
Abstract: Polycrystalline InSb thin films have been prepared by two-source thermal evaporation method. The as-deposited randomly oriented thin films develop (111) preferred orientation upon heat treatment of different maximum setting temperatures, T(max)s. Under different T(max)s, the elongate (111) grains rotate gradually the direction of the elongation respect to the thermally oxidized Si(100) substrate. The (111) preferred orientation has been seen from both cross-sectional TEM and X-ray diffraction patterns. The electrical mobility value of the thin film has been measured by the Van der Pauw’s method. A dramatic increase in the electrical mobility from few thousands, for the as-deposited film, to intermediate values of 15,000-30,000 cm2/v-s and the highest value of 36,000 cm2/v-s for thin films subjected to different T(max)s, can be correlated well to the corresponding microstruetures.