Showing papers on "Van der Pauw method published in 1988"

GaAs/(In,Ga)As, p‐channel, multiple strained quantum well field‐effect transistors with high transconductance and high peak saturated drain current

Abstract: GaAs/In0.2 Ga0.8 As structures with two paralleled 10 nm quantum wells, modulation doped from the top, bottom, and middle with Be, have been fabricated into multiple strained quantum well field‐effect transistors (MQWFET’s) with 1×150 μm2 Ti/Au gates and examined both illuminated and in the dark at 300 and 77 K. Measurements on van der Pauw structures fabricated simultaneously with the transistors showed hole mobilities and sheet carrier densities to be 200, 3100, and 8040 cm2/V s, and 5.7×1012, 1.8×1012, and 1.5×1012 cm−2 , at 300, 77, and 4 K, respectively. Shubnikov–de Haas measurements made below 4 K verified the existence of a double‐channel two‐dimensional hole gas with a strain‐shifted light‐hole ground state in the quantum wells with an effective hole mass of 0.15 me . A representative p‐channel MQWFET showed well‐saturated common‐source output characteristics, both illuminated and unilluminated, at all measurement temperatures. Measured peak extrinsic transconductances and peak saturated drain currents for the unilluminated 1 μm device were 31 and 60 mS/mm and 27 and 67 mA/mm, at 300 and 77 K, respectively.

Thermal neutron irradiation experiments on 10BP single-crystal wafers☆

Abstract: The electrical properties of 10 BP wafers grown by chemical vapour deposition at room temperature before and after irradiation by thermal neutrons were measured by the van der Pauw method. No appreciable change in electrical properties was observed for the (100) wafer. In the case of the (111) wafer, the carrier concentration for the n type increased and decreased for the p type after irradiation with thermal neutrons owing to the formation of donors caused by nuclear reaction of 10 B(n,α) 7 Li. The electrical conductivity σ, the carrier concentration n and the mobility μ of the (111) wafer after irradiation were measured at high temperatures: n decreased and μ increased for the p type (and vice versa for the n type) compared with the values before irradiation. The temperature dependence of carrier concentration before and after irradiation was correlated with the theoretical curves to calculate the donor and acceptor concentrations and their activation energies.

Molecular beam epitaxial growth and characterization of 2‐in.‐diam Hg1−xCdxTe films on GaAs (100) substrates

Abstract: Hg1−xCdxTe films with 2 in. diameters have been grown by molecular beam epitaxy on GaAs (100) substrates. These films were grown in both the (100) and (∼(111)) B crystallographic orientations and in both conduction types. They were characterized by in situ electron diffraction, infrared absorption, and van der Pauw dc Hall measurements. Their surfaces were shiny and mirrorlike from center to edge. The Cd concentrations (x) of these films were very uniform, exhibiting standard deviations (Δx) as low as 0.7% of the mean (x). Their thicknesses also were uniform within 0.6%. These films were completely uniform in their conduction types; that is, the n‐type films were entirely n type, and likewise for the p‐type films. The Hall mobilities of these films show them to be of high quality, with values as high as 6.7×102 cm2 V−1 s−1 for the p‐type (x=0.22) and 1.8×105 cm2 V−1 s−1 for the n‐type films (x=0.21). These results represent an important achievement toward the future of infrared detector technology.

Method of measuring resistivity, and apparatus therefor

Abstract: A method and apparatus for measuring resistivity employing the four-point probe method to measure the surface resistivity or volume resistivity of a sample. The method includes inputting sample shape information and calculating a resistance correction coefficient (F;FP) for the sample. The sample surface resistivity or volume resistivity is calculated by multiplying a resistance value by the correction coefficient. The apparatus includes an input unit (51) for inputting sample shape information, a unit for designating a measurement position on the sample, a unit (50) for calculating a correction coefficient, a four-point probe. (56) including four colinear electrodes (11,12,13,14), a detecting unit (55) for passing a predetermined current through the two outer (11,14) electrodes and detecting a potential difference across the two inner electrodes (12,13), a unit for calculating a resistance value and a unit for calculating the sample surface resistivity or volume resistivity:

Heavily Si‐doped GaAs grown by metalorganic chemical vapor deposition

Abstract: Heavily Si‐doped GaAs layers were grown by a metalorganic chemical vapor deposition method using disilane (Si2H6) as a silicon dopant source gas. The grown layers were characterized by the van der Pauw, secondary ion mass spectroscopy, and low‐temperature Fourier transformation infrared spectroscopy (FTIR) method. The carrier concentration has no growth temperature dependence from 550 to 700 °C temperature range. However, it has temperature dependence below 550 °C and above 700 °C. The carrier concentration of Si‐doped GaAs is usually saturated at 6×1018 cm−3 level. Further, Si doping makes the carrier concentration decrease. By using the low‐temperature FTIR method, absorption bands for SiGa, SiAs, SiGa‐SiAs pair, and lower energy bands (374 and 369 cm−1) were observed in heavily Si‐doped GaAs. The peak intensity for SiGa is smaller than that for SiAs, and the peak heights at 374 and 369 cm−1 are relatively larger than that for the other peaks. These facts suggest that, in heavily Si‐doped GaAs, a part o...

Properties of substitutionally doped Cd1−xMnxTe films and Cd1−xMnxTe–CdTe quantum well structures

Abstract: The successful substitutional doping of thin films of the diluted magnetic semiconductor Cd1−xMnxTe is discussed. These doped films were prepared using a new technique, photoassisted molecular‐beam epitaxy, in which the substrate is illuminated during film growth. In and Sb were used as n‐ and p‐type dopants, respectively. Cd1−xMnxTe:In–CdTe and Cd1−xMnxTe:Sb–SdTe superlattices were also prepared. The structural, electrical, and optical properties of the samples were studied by means of double‐crystal x‐ray diffraction, van der Pauw Hall‐effect measurements, low‐temperature photoluminescence, and piezoreflectance measurements.

Properties of doped CdTe films grown by photoassisted molecular-beam epitaxy

Abstract: Photoassisted molecular‐beam epitaxy (PAMBE) has been employed to grow a series of undoped and doped CdTe films. In and Sb were used as n‐type and p‐type dopants, respectively. The PAMBE‐grown epilayers exhibit outstanding electrical, optical, and structural properties as determined by van der Pauw Hall‐effect, low‐temperature photoluminescence, and double‐crystal x‐ray rocking curve measurements, respectively.

Elimination of slip lines in capless rapid thermal annealing of GaAs

Abstract: A new rapid thermal annealing (RTA) procedure has been developed that eliminates the problem of crystallographic slip in 2 in, ion-implanted GaAs wafers This annealing arrangement is easy to implement and is reliable A precision machined graphite support structure and guard ring are used to insure uniform cooling across the entire wafer, thus eliminating slip line production Characteristics of silicon ion implants have been determined using van der Pauw Hall, Polaron C–V profiling, and eddy current resistivity measurements Characterization showed excellent dopant activation and uniformity can be achieved using this new technique Low-temperature photoluminescence measurements were performed on samples annealed with and without graphite in the system, and no detectable difference in surface carbon contamination was found

Chromium-doped p-type semi-insulating InP

Abstract: The authors have grown p-type semi-insulating (SI) InP ingots co-doped with a shallow acceptor (Hg or Cd) and chromium as a deep donor. The compensation mechanism is the following: the holes due to the shallow acceptor are compensated by the chromium-related deep donor level. The crystals have been characterised by spark-source mass spectrometry (SSMS), secondary-ion mass spectrometry (SIMS), the temperature-dependent Hall (TDH) effect using the Van der Pauw technique and electron paramagnetic resonance (EPR). Deduced from the activation energy measurements, the donor deep level of chromium Cr3+/Cr4+ has been found at Ev+0.56 eV. SIMS depth profiles, on such SI substrates annealed at 750 degrees C, show that iron and chromium thermal stabilities are very similar.

Van der Pauw measurement of metal fibre orientation in a plastic-metal composite

Abstract: Stainless steel fibres in ABS plastic form a composite with an anisotropic resistivity. Samples are rectangular shapes with uniform thickness. By assuming two principal resistivities and by using van der Pauw's technique, we findϱ 2 =ϱ x ϱ y . For rectangular samples, field theory determinesϱ y /ϱ x and hence fibre direction. Results for three sample geometries agree with the theoretical predictions of the fibre patterns and with X-ray data. Samples formed by a centre-sprue feed are the best for fabricating large, uniform samples, while samples with a large length-to-width ratio have the most uniform metal density and fibre orientation. Resistivity was also measured by the more-common two-probe technique. Results correlate well to van der Pauw data, with 95% confidence.

Optical, electronic and magnetic properties of the dilute magnetic semiconductor Mn:CuInTe 2

Abstract: CuInTe2 and CuInSe2 are direct bandgap ternary chalcopyrite (I-III-VI2) semiconductors which are the simplest ternary analogs of the II-VI zincblende compounds. Some of the chalcopyrites exhibit nonlinear optical properties which make them good candidates for optical device technology. We have done preliminary studies on the influence of Mn2+ on the optical, transport and magnetic properties of CuInTe2 in analog to previous stud-ies of Mn:CdTe etc. Bulk polycrystalline p-type samples, with up to 12% Mn substi-tution, have been examined with polarized light microscopy, x-ray energy dispersive analysis, optical spectrometry, van der Pauw technique and SQuID magnetometer mea-surements. From the metallurgical studies, Mn is found to substitute for Cu but not In. The bandgap of Mn:CuInTe2 is larger than 0.92 eV. Most of our samples show phonon limited mobility, with the highest mobility occurring at ≈75K. Without Mn substitu-tion, CuInTe2(Se2) is diamagnetic. Samples with 3% Mn substitution in Cu sites are paramagnetic. At higher Mn concentration (3% < x < 12%), the (Cu1-xMnx)InTe2 sam-ples show antiferromagnetic coupling and a measured effective magnetic moment up to ≈5.4 μB/Mn atom. Samples with attempted Mn substitution in In sites (from 3% to 9%) show anomalous magnetic behavior at low temperatures.

Van Der Pauw Measurements of Resistivity in Plastic/Metal Composites

Abstract: The van der Pauw (VdP) technique provides a four-probe measurement of a sample's average resistivity. It is generally applied to samples which have a uniform density and thickness but an arbitrary shape. We apply the VdP method to a metal/plastic composite. Samples are cut into rectangular shapes, but internally the metal structure is a random shape. Values of resistivity correlate well (> 90%) to values measured by a two-probe technique. We can determine a composite's structure in a highly accurate though destruc tive manner. Some in-situ test applications are proposed.

Reduction Of Surface Leakage Current In Cd 0.2 Hg 0.8 Te Photodiode

Abstract: The surface leakage current of Cd0.2 Hg0.8Te photodiodes has been reduced by forming a wide gap epitaxial layer on the surface. CdHgTe double-layers consisting of p-CdxHgl_xTe (x>0.2)/p-Cd0.2Hg0,8Te were grown by liquid phase epitaxy on CdTe substrates. The hole carrier concen 3tration and m 1obility, obtained from van der Pauw Hall measurement at 77K, were 9x1015cm-3 and 6x102cm2V-15-, respectively. The p-n junctions were formed by removing the wide gap layer of 100/i m diameter to reach p-Cd0.2Hg0.8Te followed by the Indium diffusion in p-Cd0.2Hg0.8Te. The R0A products of the photodiode with and without the wide band gap layer were 9.1Q cm 2 (λ c=11μ m) and 2.00 cm2 (λ c=10μ m) at 77K, respectively, which confirm the effect of the wide gap layer on the surface leakage current reduction.

Very Heavily Doped N-Type GaAs Obtained With Pulsed Laser Annealing

Abstract: A study of carrier activation and mobility was performed in pulsed laser annealed samples of GaAs implanted with doses of Si and Se from 2.2x1012 to 6.0x1014 cm-2. The samples were annealed using a pulsed XeCl excimer laser ( λ=308 nm) and a pulsed dye laser ( λ=728 nm) with energy densities from 0.1 to 0.9 J/cm2 and a 10 nsec pulse. Very high carrier concentrations of 3x1019 and 1.5x1019 cm-3 were obtained for best n-type GaAs samples annealed with the dye laser and excimer laser, respectively. Dye laser consistently produced higher activation than excimer laser annealing. A transient reflectivity experiment was performed to identify the GaAs melt threshold and the melt phase dynamics of the GaAs,under the nitride cap. The threshold energies for cap damage were 0.34 and 0.12 J/cm2 for excimer and dye lasers, respectively. High carrier activation, as measured by Van der Pauw method, was achieved even for lightly doped samples although the room temperature Hall mobility was low. Raman spectroscopy was used to identify the threshold energies for the GaAs implant layer recrystallization and for optimum carrier activation.

Thermal Neutron Irradiation Experiments on 10BP Single-Crystal Wafers.

Abstract: The electrical properties of 10 BP wafers grown by chemical vapour deposition at room temperature before and after irradiation by thermal neutrons were measured by the van der Pauw method. No appreciable change in electrical properties was observed for the (100) wafer. In the case of the (111) wafer, the carrier concentration for the n type increased and decreased for the p type after irradiation with thermal neutrons owing to the formation of donors caused by nuclear reaction of 10 B(n,α) 7 Li. The electrical conductivity σ, the carrier concentration n and the mobility μ of the (111) wafer after irradiation were measured at high temperatures: n decreased and μ increased for the p type (and vice versa for the n type) compared with the values before irradiation. The temperature dependence of carrier concentration before and after irradiation was correlated with the theoretical curves to calculate the donor and acceptor concentrations and their activation energies.

Rapid thermal annealing of Be implanted GaAs

Abstract: Rapid thermal annealing is used to activate shallow-Be-implanted in GaAs. A proximity annealing technique is used which minimizes As evaporation. Because the substrate is left capless during annealing, surface interaction with the cap and interfacial stress are relieved. Surface morphology and Be redistribution during annealing are analyzed by scanning electron microscopy and secondary ion mass spectroscopy, respectively. Electrical characterization of the activated implant is achieved by means of a rapid thermally alloyed Au-Zn-Au contact using Van der Pauw patterns and the transmission line method. Nearly 100% implant activation and ohmic contacts are achieved. >

Measuring method of channel length of mosfet

Abstract: PURPOSE:To measure the channel length of a single MOSFET, and to measure the channel length with a high accuracy even with respect to MOSFETS, in which different errors are generated, by directly obtaining the sheet resistance of a channel by using a van der Pauw's resistor. CONSTITUTION:The sheet resistance value rhoc of a channel is measured by employing a van der Pauw's resistor while the total resistance value Rt of an MOSFET is measured from the quantity of currents flowing by applying constant voltage to the MOSFET, and the external resistance value Re and channel-length error L of the MOSFET are calculated by formulae I-III from these sheet resistance value frhoc and total resistance value Rt and previously given channel width We and channel length Lm on a mask, thus acquiring channel length Le. Where A in formulae represents a constant. Since the measuring method of channel length is constituted as mentioned above, the effect of the limitation of gate length and the dispersion of the error L is eliminated by directly measuring the sheet resistance value rhoc by using a Van der Pol resistor, thus simplifying the measurement of sheet resistance, then improving accuracy thereof.

A Microelectronic Test Structure For Thickness Determination Of Homogeneous Conducting Thin Films In VLSI Processing

Abstract: This paper describes a new test structure for use in determining the thickness of a uniform conducting film. The structure incorporates the van der Pauw cross method to determine the effective sheet resistance of a vertical, uniformly doped cross section of a polysilicon film and a bridge resistor to determine thickness of the film. By using a composite structure, which consists of the vertical cross structure and a conventional planar cross-bridge test structure, it is possible to obtain the thickness, linewidth, and resistivity of a conducting line.

Nonuniformity-induced error in mask misregistration test structures

Abstract: A performance comparison of two common misregistration test structures, the alignment resistor and the modified van der Pauw structure, incorporated adjacent to one another in a test chip for three separate fabrication runs, is presented. The results indicate that the modified van der Pauw structure consistently provides a more accurate measurement of the misregistration for the test structure sizes and fabrication process used. Errors introduced by lateral variation in sheet resistance and linewidth within each test structure are discussed. >