Showing papers on "Van der Pauw method published in 1982"

Platinum silicide ohmic contacts to shallow junctions in silicon

Abstract: Ohmic contact to shallow pn+ and np+ junctions in silicon were studied. Thin layers (∼200 A) of platinum were sputter deposited and reacted with the silicon substrate at 590 °C to result in the stable PtSi silicide. In a self‐registered process, aqua regia was used to etch the unreacted platinum. An Al‐0.9% Si alloy has been used for final metallization. A small contact area of 3×3 μm2 was chosen so as to be in accordance with the current level of integration. A four‐terminal Kelvin‐resistor structure has been utilized to accurately measure the contact resistance. The effect due to the dopant concentration was studied at the implant dose range of 1–8×1015 cm−2. Van der Pauw sheet resistance measurements, secondary ion mass spectroscopy, and Rutherford backscattering experiments were all performed in order to characterize the shallow junctions and the silicide‐silicon interface. Predeposition and in‐situ etching resulted in considerable improvement in the measured specific contact resistance. Values well w...

Donor energy level for Se in Ga1−xAlxAs

Abstract: Electrical properties and the donor energy level in Se‐doped n‐Ga1−xAlxAs (0⩽x⩽0.82) prepared by metalorganic chemical vapor deposition have been investigated. The van der Pauw technique was used to measure the electrical properties of n‐Ga1−xAlxAs. The resistivity and electron concentration of Se‐doped Ga1−xAlxAs were found to be strongly affected by the donor energy level for Se. The donor energy levels ED of Se in Ga1−xAlxAs was found to remain constant at 0.003 eV for x<0.25. For x≳0.25, ED takes the form of an inverted V with a maximum at the direct‐indirect band crossover.

28Si implantation into 40Ar implant‐pretreated semi‐insulating GaAs substrates—mobility and activation efficiency enhancement

Abstract: We describe a 750‐keV, 5–10×1012 cm−2 dose, 40Ar implant pretreatment for semi‐insulating (SI) GaAs substrates allowing generation of 28Si implanted n layers with higher mobility and/or activation efficiency. This effect was observed in Bridgman Cr‐doped, Bridgman Cr‐O‐doped, liquid encapsulated Czochralski (LEC) Cr‐doped, and LEC undoped substrates. Pretreated and control samples were studied by carrier profiling, van der Pauw measurements, and secondary ion mass spectrometry (SIMS). The compensation ratio (ϑ = NA/ND) of n layers in pretreated substrates was lower than in controls. Probable mechanisms of improvement in ϑ are (1) reduced surface Cr concentration due to pretreatment, (2) preferential incorporation of 28Si on Ga sites due to pretreatment‐created stoichiometry imbalance, and (3) a combination thereof.

The electrical properties of pbte implanted with H+ As+ or Sn+

Abstract: The van der Pauw technique has been used to make measurements of the electrical resistance, Hall mobility and carrier concentration of ion-implanted lead telluride at 77 K. Small changes in the electrical properties were observed for relatively large changes in the implantation parameters. A previously unreported room temperature annealing process was found to produce large increases in carrier concentration in samples bombarded with protons of low energy (∼50 keV). This annealing effect appears to be due to the loss of lead vacancies by migration out of the bombarded region to either the surface or the bulk of the sample.

Comment on ’’Generalized Hall‐effect measurement geometries and limitations of van der Pauw‐type Hall‐effect measurements’’

Abstract: The general validity of the van der Pauw‐Hall measurement technique for arbitrarily shaped samples has recently been disputed, and the claim has been made that the samples must have mirror symmetry. Here, it is shown that the analysis leading to the mirror symmetry requirement is more restrictive than necessary and that arbitrary shapes can be used. It is also shown that even with nonsymmetric shapes, magnetoresistance effects are eliminated by reversing the magnetic field and averaging the data.

High-magnetic-field Van der Pauw method Magnetoresistance measurement and applications

Abstract: The paper develops a simple theory to account for the magnetoresistance influence on Van der Pauw-type experiments (i.e. resistivity and Hall coefficient RH measurements in arbitrarily shaped samples). In particular, it is proved that the voltage developed between two nonsuccessive contacts includes not only the usual Hall term (involving the magnetic field and RH) but also an additional term proportional to the magnetoresistance coefficient. This term is especially important under high magnetic fields and in anisotropic or ambipolar semiconductors; if ignored, it will be responsible for misleading interpretations of the Hall coefficient behaviour. Moreover, the influence of contact dimensions is shown to result mainly in an erroneous term, proportional to the Hall voltage. In this new light averaging techniques, suitable for more accurate measurements, are proposed. The experimental results fully support the theoretical derivations. As an application, a powerful method for the characterisation of ambipolar semiconductor slabs with arbitrary geometry is presented.

Growth And Characterization Of GaAs, GaInAs, and GaInAsP for microwave applications

Abstract: Vapor-phase epitaxy (VPE) systems for the growth of 1) GaAs on Cr-doped GaAs substrates, and 2) lattice matched GaInAs and GaInAsP on Fe-doped InP substrates are briefly described. Layer composition of the ternary and quaternary compounds were measured by electron probe microanalysis, lattice mismatch by X-ray diffractometry, average carrier concentration and mobility determined using the Van der Pauw technique. Carrier profiles were investigated using an electro-chemical profiler. Several hundred n-type Ga0.47In0.53As/InP structures have been grown and characterized. Unintentionally-doped layers with a carrier concentration of 2x1015cm-3 and μ(300) and μ(77) of 11x103 and 38x103cm2V-ls-1, respectively, were realized. These represent the highest mobility values reported for VPE Ga0.47In0.53As at this doping level. Se-doped n-layers ranging in thickness from 0.2 to several μm and with carrier density from 1x1016 cm to 3x1018cm-3 + were grown. n-n structures with sharp n+-n transitions were grown for device fabrication studies. The doping profile of a 2 cm x 1 cm ternary layer grown using a rotating substrate holder was found to be fairly uniform; this n+-n wafer had an n+-layer doping of 1.6±0.1x1018cm-3, n+-layer thickness of 0.31±0.01 μm, n-layer doping of 9.5±0.5x101bcm-3, and n-layer thickness of 0.3±0.03 μm. The mobility profile of submicrometer n-layers was measured using the differential Van der Pauw technique. The high mobility was found to be maintained down to the ternary-substrate interface.© (1982) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Flame Annealing of Ion Implanted Silicon

Abstract: The authors investigated flame annealing of ion implantation damage (consisting of amorphous layers and dislocation loops) in (100) and (111) silicon substrates. The temperature of a hydrogen flame was varied from 1050 to 1200/sup 0/C and the interaction time from 5 to 10 seconds. Detailed TEM results showed that a defect-free annealing of amorphous layers by solid-phase-epitaxial growth could be achieved up to a certain concentration. However, dislocation loops in the region below the amorphous layer exhibited coarsening, i.e., the average loop size increased while the number density of loops decreased. Above a critical loop density, which was found to be a function of ion implantation variables and substrate temperature, formation of 90/sup 0/ dislocations (a cross-grid of dislocation in (100) and a triangular grid in (111) specimens) were observed. Electrical (Van der Pauw) measurements indicated nearly a complete electrical activation of dopants with mobility comparable to pulsed laser annealed specimens. The characteristics of p-n junction diodes showed a good diode perfection factor of 1.20-1.25 and low reverse bias currents.

A comment on "An extension and application of the Thompson-Lampard theorem"

Abstract: This letter proves that the conductivity measuring technique presented by Rehman-Murti can be directly derived from the Van Der Pauw's method by a simple transformation of the current field. Hence, conclusions obtained for one method can be transposed to the other one. It is also proved that the Rehman-Murti structure can also be applied to Hall mobility measurements.

Applicability of the Method of VAN DER PAUW to Samples with Two-dimensional Defects

Abstract: The influence of cleavage steps and low angle boundaries on the results of conductivity and Hall measurements by Van der Pauw's method are investigated and some criterions for evidence of sample inhomogeneities by the assumption of symmetrical sample shape and contact arrangement formulated. Hall voltage is less influenced by cleavage steps, so that the determination of carrier concentration is nearly correct also in strongly disturbed samples. Conductivity and carrier mobility measurements in the usus usual calculation procedure will lead to considerable errors. By one pair of contacts only for conductivity as well as for Hall measurements, the influences of inhomogeneities cannot be distinguished from volume effects of the sample.

Analysis of defect structure in silicon. Effect of grain boundary density on carrier mobility in UCP material

Abstract: The relationships between hole mobility and grain boundary density were studied Mobility was measured using the van der Pauw technique, and grain boundary density was measured using a quantitative microscopy technique Mobility was found to decrease with increasing grain boundary density

Thin film cadmium telluride solar cells

Abstract: Cadmium telluride films have been deposited on foreign substrates by the direct combination of the vapors of the elements in a hydrogen atmosphere. The importance of controlling the Cd/Te molar ratio in the reaction mixture to obtain nearly stoichiometric films was established. The properties of nearly stoichiometric films on mullite substrates were measured by the van der Pauw technique in the temperature range of 25/sup 0/-150/sup 0/C. The current-voltage characteristics of Ag/n-CdTe/W/graphite and Ag/ p-CdTe/W/graphite structures indicate that the CdTe/substrate interfaces are of high resistance. The interface resistance can be reduced substantially by using an In or Sb interlayer to form heavily doped regions. The deposition of p-type cadmium telluride films by using arsine or phosphine as a dopant was studied in detail. The recrystallization of cadmium telluride films by a Nd:YAG laser was investigated. Schottky barrier solar cells were prepared from ntype cadmium telluride films and heterojunction cells from p-type cadmium telluride films.