Showing papers on "Van der Pauw method published in 1989"
TL;DR: A modulation-doped Al0.35Ga0.65As/GaAs single interface structure with a 700 A undoped setback grown by solid-source molecular beam epitaxy (MBE) shows a Hall mobility of 11.7×106 cm2/V at a carrier density of 2.4×1011 electrons/cm2 measured in van der Pauw geometry after exposure to light at 0.35 K as mentioned in this paper.
Abstract: A modulation‐doped Al0.35Ga0.65As/GaAs single interface structure with a 700 A undoped setback grown by solid‐source molecular beam epitaxy (MBE) shows a Hall mobility of 11.7×106 cm2/V s at a carrier density of 2.4×1011 electrons/cm2 measured in van der Pauw geometry after exposure to light at 0.35 K. This is the highest carrier mobility ever measured in a semiconductor. Similar Al0.32Ga0.68As/GaAs structures with 1000–2000 A setbacks show Hall mobilities in the dark at 0.35 K as high as 4.9×106 cm2 /V s for carrier densities of 5.4×1010 electrons/cm2 and lower.
347 citations
TL;DR: In this article, the measurement errors of resistivity and Hall coefficient in the van der Pauw technique due to contact lead size or lead placement errors are calculated for square and cloverleaf-shaped samples, and compared to the results for a simple circular disk.
Abstract: The measurement errors of resistivity and Hall coefficient in the van der Pauw technique due to contact lead size or lead placement errors is calculated for square and cloverleaf‐shaped samples, and compared to the results for a simple circular disk. Both the square and the cloverleaf greatly reduce these errors, compared to the circular sample shape. Another source of measurement error, sample inhomogeneity, is also analyzed, and it is shown that the error introduced by inhomogeneities is proportional to E2 in the region of the inhomogeneity. Consequences of these results are discussed.
93 citations
TL;DR: In this paper, the measurement error of the resistivity due to contact displacement was determined on samples of six different shapes: circle, square, two circular cloverleafs, and two square clover leaf shapes.
Abstract: Van der Pauw resistivity measurements were performed on samples of six different shapes: circle, square, two circular cloverleafs, and two square cloverleafs, and the measurement error of the resistivity due to contact displacement was determined. Earlier predictions for this error were verified for the circle and square, and two circular cloverleafs, although significant higher‐order corrections were found in all cases except the square. The three square shapes gave contact placement errors typically 10–100 times smaller than the errors in the corresponding circular shapes. All cloverleafs gave smaller errors than the corresponding nonclovered shapes, although this difference disappeared in the limit of large contact displacement.
37 citations
TL;DR: In this article, a straightforward extension of the van der Pauw calculation is presented, which allows a determination of the Hall coefficient from quantities measured in one field direction only, and is used for the measurement of resistivities and Hall coefficients.
Abstract: The van der Pauw geometry has been widely used for the measurement of resistivities and Hall coefficients. Although the measurement of a Hall coefficient requires a finite magnetic field, it should be noted that van der Pauw’s expression is valid only in the limit of zero field; in addition to the Hall contribution, measurements in a finite magnetic field generally include a term associated with field‐induced changes in the longitudinal resistivity. Although a simple solution to this problem entails taking the difference between readings in opposite field directions, there are circumstances where this may be impractical. In this note we present a straightforward extension of the van der Pauw calculation which allows a determination of the Hall coefficient from quantities measured in one field direction only.
17 citations
TL;DR: In this paper, the authors used reflection high-energy electron diffraction (RHEED) oscillations to study the growth condition dependence of the growth of pseudomorphic InGaAs layers on GaAs, as well as van der Pauw/Hall measurements to evaluate the growth parameter dependence of electrical properties of InGaA/AlGaAs high electron mobility transistor structures.
Abstract: We use reflection high‐energy electron diffraction (RHEED) oscillations to study the growth condition dependence of the growth of pseudomorphic InGaAs layers on GaAs, as well as van der Pauw/Hall measurements to evaluate the growth parameter dependence of the electrical properties of InGaAs/AlGaAs high electron mobility transistor structures. We present our conclusions regarding growth conditions for which smooth RHEED oscillations can be obtained, and the parameters for which optimal electrical properties can be reached.
15 citations
TL;DR: In this article, the structural properties of the films were investigated by X-ray diffraction measurements and the morphology of the film was investigated with a scanning electron microscope with optical reflectance and transmittance measurements in the wavelength range 0.3-0.8 μm.
12 citations
TL;DR: In this article, the dependence of zero magnetic field resistivity as well as low magnetic field Hall and magnetoresistance coefficients of undoped polycrystalline bismuth films on thickness and doping concentration in the temperature interval from 100 to 300 K was investigated.
Abstract: An investigation is made of the dependence of zero magnetic field resistivity as well as low magnetic field Hall and magnetoresistance coefficients of undoped as well as Te-, Sn-, and Ga-doped polycrystalline bismuth films on thickness and doping concentration in the temperature interval from 100 to 300 K. The films are deposited onto amorphous substrates by means of simultaneous thermal evaporation from two different sources for the host and dopant material, respectively. Doping does not alter the structure of the films significantly. The galvanomagnetic measurements are carried out using van der Pauw's technique with the magnetic field perpendicular to the film plane.
Der spezifische Widerstand in Abwesenheit eines Magnetfeldes sowie die Hall- und Magnetowiderstandskoeffizienten im schwachen Magnetfeld von undotierten sowie von Te-, Sn- und Ga-dotierten polykristallinen Wismutschichten werden in Abhangigkeit von der Schichtdicke und der Dotierungskonzentration bei Temperaturen zwischen 100 und 300 K untersucht. Die Beschichtung erfolgt auf amorphen Substraten durch gleichzeitige thermische Verdampfung aus zwei unterschiedlichen Quellen fur das Wirts- bzw. Dotierungsmaterial. Die Dotierung verandert die Schichtstruktur nicht signifikant. Die galvanomagnetischen Messungen werden mit der van der Pauwschen Methode in einem senkrecht zur Schichtebene gerichteten Magnetfeld durchgefuhrt.
11 citations
TL;DR: In this paper, the van der Pauw theorem is applied for electrical characteristic measurements on anisotropic conductors in applied magnetic fields and the relations among the resistances defined as the potential difference between the remaining contacts per unit current are presented for various combinations of current contacts.
Abstract: A two‐dimensional anisotropic medium with a resistivity tensor in the general form is considered. In the arbitrarily shaped region with four point contacts on the circumference, the potential problem caused by two current contacts is solved by using affine and conformal mappings. The relations among the resistances that are defined as the potential difference between the remaining contacts per unit current are presented for various combinations of current contacts. The resistance characteristics in this paper include the well‐known van der Pauw theorem, which is applicable for electrical characteristic measurements on anisotropic conductors in applied magnetic fields.
10 citations
TL;DR: In this article, a Van der Pauw structure on GaAs/AlGaAs modulation-doped layers was constructed using x-ray nanolithography, evaporation, and liftoff.
Abstract: We have built four‐probe Van der Pauw structures on GaAs/AlGaAs modulation‐doped layers. On top of the 4×4 mm active area we fabricated a 200 nm period Ti/Au Schottky metal grid‐gate using x‐ray nanolithography, evaporation, and liftoff. Electrons traveling from one contact to the other suffer electron back diffraction at specific gate voltages resulting in transconductance oscillations. Magneto‐capacitance measurements indicate two sets of quantum oscillations corresponding to the charge density under and in‐between the Schottky metal lines. Far infrared cyclotron resonance measurements show a shift in the resonance peak as a function of gate bias.
8 citations
TL;DR: In this paper, a simple averaging and sampling procedure is suggested to suppress this type of behavior and is found to be sufficient to obtain reliable and repeatable Hall voltages and coefficients.
Abstract: It is shown that care must be exercised in using digital equipment when making Hall measurements in a van der Pauw setup employing the ASTM standard method. This arises because of quantization error when working near the sensitivity limit of the equipment. For materials with small Hall mobilities (<100 cm2/V s) this can lead to an incorrect specification of the carrier type and inconsistent mobility behavior. A simple averaging and sampling procedure is suggested to suppress this type of behavior and is found to be sufficient to obtain reliable and repeatable Hall voltages and coefficients.
7 citations
TL;DR: In this paper, a modification-doped InyAl1−yAs/InxGa1−xAs heterostructures were grown on InP substrates by molecular beam epitaxy.
Abstract: Modulation‐doped InyAl1−yAs/InxGa1−xAs heterostructures were grown on InP substrates by molecular beam epitaxy. With the aim of increasing the InAs mole fraction of the InGaAs layer, the epilayers were intentionally lattice mismatched with respect to the substrate. The samples were characterized by optical microscopy, x‐ray analysis, and the van der Pauw method. In a structure with x=0.68, y=0.67, and a 0.5‐μm‐thick InyAl1−yAs buffer layer, Hall mobilities as high as 13 140 cm2/V s and 78 000 cm2/V s were measured at 300 and 77 K despite an estimated dislocation density of 2×105 cm−1 in a 〈110〉 direction at the substrate‐epilayer interface.
TL;DR: In this article, photo assisted molecular beam epitaxy was used for the preparation of p-type CdTe epilayers and modulation-doped HgCdTe multilayers in which arsenic is used as the substitutional dopant.
Abstract: We report the successful use of photoassisted molecular‐beam epitaxy for the preparation of p‐type CdTe epilayers and p‐type modulation‐doped HgCdTe multilayers in which arsenic is used as the substitutional dopant. The CdTe:As epilayers were grown at substrate temperatures which ranged from 230 to 180 °C. The resulting CdTe:As layers exhibited room‐temperature hole concentrations ranging from 7×1015 to 6.2×1018 cm−3, as determined by van der Pauw Hall effect measurements. This highest doping level is nearly two orders of magnitude greater than that obtained for bulk p‐type CdTe. The mobility of the CdTe:As epilayers ranged from 27 to 74 cm2/V s, at room temperature. The arsenic acceptor ionization energy in CdTe:As was found to be ∼58–60 meV using low‐temperature photoluminescence measurements. The modulation‐doped HgCdTe samples exhibited hole concentrations ranging from 5×1016 to 1×1018 cm−3 and hole mobilities of ∼200–325 cm2/V s at temperatures <200 K.
TL;DR: In this paper, a conformal mapping method was used to map out the equipotential and current stream lines for an arbitrary Hall plate with van der Pauw geometry by reformulating the Schwarz-Christoffel equation in a form most convenient for computation.
Abstract: We show how the conformal mapping method can be used to map out the equipotential and current stream lines for an arbitrary Hall plate with van der Pauw geometry by reformulating the Schwarz–Christoffel equation in a form most convenient for computation. Our numerical technique is then used to determine the potential and current distributions in a AlxGa1−x As/GaAs heterostructure with parallel conduction. Our results for a single layer agree with experimental observations at low magnetic field and for regions between the plateaus of the quantum Hall effect. Equipotential and current stream lines are obtained for two previously proposed models for the heterostructures with parallel conduction: the two‐band model and the isolated layer model. In the case of a large Hall angle (near the plateau of the quantum Hall effect) singularities of electric fields occur around the source‐drain contacts as in a standard Hall bar. For the isolated layer model, additional singularities are formed around the side contacts...
TL;DR: In this paper, a simple experimental method for determination of the Hall constant based on a continuous temperature variation is proposed, which is convenient in the van der Pauw configuration, particularly for samples with asymmetrically positioned contacts, and for materials with a low mobility of free carriers.
Abstract: A simple experimental method for determination of the Hall constant based on a continuous temperature variation is proposed. Measurements made with the procedure described are proven to be fast and accurate. Its basic advantages are simplicity and the ability to measure a larger number of points in a considerably shorter time than the standard method without a significant reduction in accuracy. It is convenient in the van der Pauw configuration, particularly for samples with asymmetrically positioned contacts, and/or for materials with a low mobility of free carriers.
TL;DR: In this paper, the authors report the results of conductivity and mobility profiles of expitaxial layers of Cd/sub chi/Hg/sub 1-chi/Te at 300 and 77 {Kappa} obtained using the step and etch technique.
Abstract: The authors report the results of conductivity and mobility profiles of expitaxial layers of Cd/sub chi/Hg/sub 1-chi/Te at 300 and 77 {Kappa} obtained using the step and etch technique. In this technique, layers are sequentially stripped through chemical etching and differential Hall measurements are performed in the van der Pauw configuration.
13 Mar 1989
TL;DR: In this article, the bottom and cross sectional dimensions of a metal-oxide semiconductor (MOS) gate based on measuring the inversion layer linewidth are characterized.
Abstract: A novel technique is presented to characterize the bottom and cross sectional dimensions of a metal-oxide semiconductor (MOS) gate based on measuring the inversion layer linewidth. The results presented are taken from a structure fabricated in the Stanford 2- mu m BiCMOS process. Analysis of test results revealed undesirable influences from three identifiable sources. Two are a result of different sheet resistances between the van der Pauw and Kelvin line portions of the structure. The third is due to small DVM currents, which drop a small voltage in the taps of the structure. A better layout based on this understanding is proposed. The bottom dimension of the gate can potentially be used in conjunction with other measurements of the gate, such as the width of the selective tungsten, in order to predict the cross-sectional shape of the gate or tungsten selectivity. >
TL;DR: In this paper, fast thermal diffusion of zinc into undoped semi-insulating GaAs substrates from spin-on zinc silica film is performed in A.G. Associates Heat pulse 410 system with tungsten-halogen lamps as the heat source.
Abstract: Rapid thermal diffusion of zinc into undoped semi-insulating GaAs substrates from spin-on zinc silica film is performed in A.G. Associates Heat pulse 410 system with tungsten-halogen lamps as the heat source. The Zn diffused layers were electrically characterised by Van der Pauw measurements and showed the formation of p + layer. The surface morphology of the diffused layers were observed by optical microscope and scanning electron microscope. The depth profiling of diffused layers by secondary ion microscopy showed considerable diffusion of Si along with Zn. Radio frequency sputter depositing Si 3 N 4 was found to be a good diffusion barrier for Zn diffussion. Non-alloyed ohmic contact with low contact resistivity was implemented on these Zn diffused layers.
02 Mar 1989-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, the authors used the van der Pauw technique to evaluate the end-of-range residual damage near the implanted layer/original crystalline interface by annealing above 550 °C.
Abstract: Silicon layers amorphized with 40-keV and 100-keV Ge+ implantations have been evaluated using Rutherford backscattering (RBS) spectrometry and the van der Pauw technique. The slight increase in RBS yield corresponding to the end-of-range residual damage is recognized near the implanted layer/original crystalline interface by annealing above 550 °C. The lower structural recovery of Ge atoms in the host lattice would arise from the difference in atomic size of both atoms. The variation of the electrical properties in the implanted layer suggests the existence of tails in the density-of-states by perturbing the band edge via a deformation potential.
TL;DR: In this paper, a modulation doped Al.65As/GaAs single interface structure using Si delta doping setback from the two dimensional electron gas (2 DEG) by 700A, was measured in van der Pauw geometry at 0.35K and showed an electron mobility of 1.17× 107 cm2/V sec at a carrier density of 2.2× 1011electrons/cm2.
Abstract: A modulation doped Al.35Ga.65As/GaAs single interface structure using Si delta doping setback from the two dimensional electron gas (2 DEG) by 700A, was measured in van der Pauw geometry at 0.35K and showed an electron mobility of 1.17× 107 cm2/V sec at a carrier density of 2.2× 1011electrons/cm2. An Al.30Ga.70As/GaAs single quantum-well 250A wide of similar structure with a 500A setback yielded a 2 DEG mobility of 5.1× 106 cm2 /Vsec at 3.0×1011 electrons/cm2under similar measurement conditions. These mobilities exceed those previously published by more than a factor of two for the single interface structure, and by nearly an order of magnitude for the quantum-well. The samples were grown by solid source MBE in a Varian Gen II modified with He closed-cycle cryogenic vacuum pumping, and in other ways, to achieve a base pressure of 1.5× 10−12 torr, as measured on a extractor-type ionization gauge that is not subject to the usual x-ray limited reading.
TL;DR: In this article, the electrical properties of dual Ge+/B+implanted layers are discussed by a two-carrier model consisting of both electron and hole, and they suggest that the lower structural recovery, 98% of Si occupies substitutional sites, arises from the difference in tetrahedral covalent radii among Si, Ge, and B atoms.
Abstract: B+‐implanted Si layers preamorphized with 100‐keV Ge+ implantation have been evaluated using Rutherford backscattering spectrometry and the van der Pauw technique. We suggest that the lower structural recovery, 98% of Si occupies substitutional sites, arises from the difference in tetrahedral covalent radii among Si, Ge, and B atoms. Electrical properties of dual Ge+/B+‐implanted layers are discussed by a two‐carrier model consisting of both electron and hole. The conversion temperature from the p‐ to the n‐type varies from ∼15 to ∼ 125 °C with increasing electrical activation of the boron acceptor. The activation saturates at annealing temperatures above 800 °C. This restriction is due to the presence of the level and/or the defect induced in the preamorphization process.
TL;DR: In this article, a seed crystal was used with helium gas for the heat exchanger and the optimum conditions for single crystal growth were determined to be growth time of 8.5 h, growth rate less than 4 mm/h and a helium flow rate smaller than 23.6 l/min.
01 Jan 1989
TL;DR: In this article, the influence of the heat treatment on the electrical properties is examined in order to study the difference between RTA and conventional thermal anneal (CTA) processes through the electrical activity of the grain boundary (GB) barriers.
TL;DR: In this paper, a spin-on source was formed in N-type GaAs by a spinon source which was rapid diffused at 950°C for 6s, and regions of P+ were formed by thermal evaporation with a base pressure of 3×10-6 Torr.
Abstract: Stable, low resistance ohmic contacts to p-type GaAs were studied for use in semiconductor laser applications. Comparison was made between Cr/Au, Au:Be and Pd/Au:Be metallizations. Regions of P+ were formed in N-type GaAs by a spin-on source which was rapid diffused at 950°C for 6s. Surface doping of 2×1020/cm3 and junction depth of 0.4μm were determined by SIMS, groove and stain, and electrochemical profile. Metallizations were accomplished by thermal evaporation with a base pressure of 3×10-6 Torr. Sintering of the metallizations was done by furnace or RTA at 350°C. This sintering temperature was selected after RBS studies predicted an absence of significant interdiffusion. Pd/Au:Be yielded the best result of 0.3μΩ-cm2 based upon transmission line, cross-bridge Kelvin and van der Pauw studies. A layer of BeO was revealed on the surface of Au:Be contacts by Auger studies. Cross-section TEM studies on Pd/Au:Be revealed a uniform layer of alloyed Ga-Au with an absence of spiking.
TL;DR: In this article, the effect of magnetic field on field effect mobility and Hall effect on thin poly(3-hexylthiophene) films was studied. But the results were limited.
Abstract: We report studies of transport properties of thin films of undoped poly(3-hexylthiophene) (P3HT) fabricated by spinning a polymer solution onto oxidised silicon or glass. The film thicknesseswere on the order of 1000 A. We studied magnetoresistance, the effect of magnetic field on field effect mobility and Hall effect. Transverse magnetoresistance was measured on films on glass. A positive anomalous magnetoresistance with a saturation value of about 0.1 % was found. Transverse magnetoresistance was also studied by measuring the change of a field effect mobility with magnetic field. This measurement was performed using the field effect transistor structure. An initial mobility of 6.5 × 10−5 cm2/Vs was reduced by about 15 % in a transverse magnetic field. We also carried out Hall effect measurements on films on glass using a Van der Pauw contact configuration. The measured Hall mobility was 2.17 × 10−5 cm2/Vs. Finally we measured the temperature dependence of the Hall mobility and found it follow the exp(T-l/4) law of variable range hopping.
Dissertation•
01 Jan 1989
TL;DR: In this article, Van der Pauw's technique was used to obtain the resistivity and the carrier concentration of electrochemically colored polycrystalline WO3 films, which revealed large variations in electrical, optical and structural properties during the electrochromic process.
Abstract: Electrochromic tungsten trioxide films of 200 to 650+20 nm thickness were deposited onto glass slides and Sn02:F substrates using spray pyrolysis. The investigations of electrochemically colored WO3 films revealed large variations in electrical, optical and structural properties during the electrochromic process. The resistivity and the carrier concentration of electrochromic W03 films were obtained by Van der Pauw's technique. The resistivities of as-prepared WO3 films deposited onto glass at substrate temperatures between 200•‹C and 400•‹C were found to be in the range of lo5 1 R-cm and decreased by 2 to 8 orders of magnitude after coloration. The carrier concentration of the colored films was estimated to be about loz1 cm". X-ray diffraction studies revealed structural changes in the polycrystalline WO3 films deposited at substrate temperatures greater than 300•‹C during the electrochromic process. The X-ray diffraction peaks for colored films could be assigned to hydrogen tungsten bronze ( HxW03 ); the structure of the bleached films reverted to the original uncolored state ( WO3 ). The reflectance properties of colored polycrystalline WO3 films can be predicted theoretically by the free electron Drude theory. Measurements of infrared reflectances showed that the polycrystalline WO3 films deposited at a higher temperature have higher infrared reflectivity. The electrons injected into such films likely show free electron behavior. Dedicated to my parents and my wife for their continual support and encouragement
TL;DR: In this article, a facility for Hall effect measurements, automated by a commercial microcomputer, was designed for the characterisation of the electrical properties of semiconductors as a function of temperature.
Abstract: The authors have designed a facility for Hall effect measurements, automated by a commercial microcomputer. The van der Pauw method has been employed. The system was designed for the characterisation of the electrical properties of semiconductors as a function of temperature. This project is proposed as a short laboratory course for physics students.
TL;DR: In this paper, the applicability of thin films of silicon separated by oxygen implantation (SIMOX) as pressure transducers in monolithic integrated-circuit technology is discussed, the buried dioxide layer formed through the deep implantation of oxygen ions giving very good isolated substrates.
Abstract: The applicability of thin films of silicon separated by oxygen implantation (SIMOX) as pressure transducers in monolithic integrated-circuit technology is discussed, the buried dioxide layer formed through the deep implantation of oxygen ions giving very good isolated substrates. Piezoresistance and Van der Pauw resistivity measurements have been carried out on several SIMOX thin films under hydrostatic pressures up to 10 kbar. The pressure coefficient was found to be closed to the typical value (2×10−3 kbar−1) in n-type diffused silicon layers but relaxation effects were observed on several samples. The time constant τ of this relaxation effect was measured to be 1 h. The results obtained on these layers under pressure are correlated with the electrical behaviour and compared with piezoresistance measurements in a single crystal and a bicrystal.
13 Mar 1989
TL;DR: In this paper, a top-contact resistor test structure was proposed to simulate the ability of a Van de Pauw test structure to provide reliable local values of the sheet resistance of a conducting film but in a plane perpendicular, rather than parallel, to the wafer surface.
Abstract: A top-contact-resistor test structure, measurements made to validate its operation, and supporting analysis for VLSI process monitoring are described. The structure was devised to simulate the ability of a Van de Pauw test structure to provide reliable local values of the sheet resistance of a conducting film but in a plane perpendicular, rather than parallel, to the wafer surface. The objective was to provide access to film thickness through electrical measurements in a manner similar to that in which the sheet resistance measurements obtained from Van der Pauw structures make linewidth measurements possible when used in conjunction with a Kelvin resistor. Resistance measurements performed with this test structure permit calculation of film thickness and bulk resistivity. >