Showing papers on "Van der Pauw method published in 1978"

An Experimental Study of Various Cross Sheet Resistor Test Structures

Abstract: Newly designed cross sheet resistors are shown to give the same (within 0.5%) measured sheet resistance as conventional van der Pauw structures. Diffused boron and phosphorus layers with sheet resistances near 200 Ω/ were studied with the sampled areas varying from a square 6.4 μm (0.25 mil) on a side to a circle 762 μm (30.0 mils) in diameter. An increase in measured sheet resistance values was observed due to surface leakage currents, and an equivalent circuit model was developed to explain the results. The effect of joule heating on measured sheet resistance values was observed in both large and small cross structures.

Analysis of symmetrical Van der Pauw structures with finite contacts

Abstract: A theory is given for Van der Pauw structures with contacts of non-zero lengths which are invariant for rotations of 90°. A general theorem has been derived. For a certain class of structures an analytical solution of the Laplace equation is obtained instead of using finite difference equations. The method leans heavily on Schwarz-Christoffel transformation techniques.

Incorporation of Sn into epitaxial GaAs grown from the liquid phase

Abstract: The incorporation of Sn into LPE GaAs was studied as a function of the atomic fractionx Sn of Sn in the liquid (1.6×10−4≤x Sn ≤0.54), the growth temperatureT K and the cooling rate α. The diffusion coefficient of As in Ga for moderate Sn-doping was deduced from the growth velocities to beD As (760° C)=(3.3±1.0)×10−5 cm2/s. The epitaxial layers were analyzed after van der Pauw with special emphasis on the sources of experimental error. With the aid of current mobility theories the concentrations of the ionized donors and acceptors were derived. From their dependence onx Sn , on α and onT K combined with the Schottky-barrier model of Sn incorporation it can be concluded that the melt and the growing crystal surface were in thermal equilibrium. The diffusion coefficient of Sn in GaAs is about 8×10−14 cm2/s at 760° C. The distribution coefficient for Sn increases from 4.4×10−5 to 12.3×10−5 in the temperature range from 690 to 800° C. The total Sn incorporationx Sn was measured using the atomic absorption spectroscopy for the first time down tox Sn =1017/cm3. From these data it can be concluded that up tox Sn =0.54 the dopant Sn is incorporated as donor and as acceptor only and that within the experimental scatter there is no indication of incorporation as a neutral species.

A van der Pauw resistor structure for determining mask superposition errors on semiconductor slices

Abstract: A symmetric eight-point van der Pauw resistor structure is described which makes it possible to determine the x - and y - axis vector components of mask superposition error on specially processed semiconductor slices. The structure is fabricated by first delineating a corner-contacted square van der Pauw resistor geometry. A second masking step adds sensor arms at the midpoints of the sides of the square body if the two masks have been correctly superimposed. The actual location of the sensor arms is determined by carrying out a series of four-point resistance measurements after doping the structure. Control geometries, in which the eight sensor arms are delineated on the same masking step, are used to investigate the accuracy and precision of the measurement technique. It is found that the vector components of mask superposition error can be determined, in the absence of mask-to-mask registration errors, with an absolute accuracy in the range ±0.10 μm and standard error below 0.015 μm. Examples of vector displacement maps are presented which illustrate the information which can be obtained when a large number of such devices is evaluated using automatic test and computing equipment.

Mobility profiling of f.e.t. structures

Abstract: Several techniques have been used to obtain electron mobility profiles in GaAs f.e.t. structures. In particular, mobilities have been measured near the interface between the active n layer and the underlying high resistivity material. The most detailed information in this region has been obtained using a Schottky-gated Van der Pauw technique.

Resistivity measurement of thin doped semiconductor layers by means of four point-contacts arbitrarily spaced on a circumference of arbitrary radius

Abstract: The resistivity of a thin doped semiconductor layer or wafer measured in the vicinity of four point contacts placed on the semiconductor surface is shown to be independent of the relative distance between the contacts, provided the contacts are located on a circumference, and the distance to the boundary of the surface will not fall short of the greatest actual spacing between contacts. This method combines the advantage of the four probe resistivity measurement originally proposed by Valdes, that is the determination of ρ in a restricted layer region, with the advantage of arbitrary spacing of the probes, which characterizes van der Pauw's method. Experiments are in agreement with results obtained by the measuring methods of Valdes and van der Pauw.

Observations of anisotropic diffused layer sheet resistance in EFG silicon ribbon solar cells

Abstract: Anisotropic electrical conductivity has been observed in the near‐space‐charge region of phosphorus‐diffused EFG silicon ribbon solar cells during the course of junction profiling studies using Van der Pauw sheet‐resistance measurement techniques. This anisotropy is believed due to either preferential diffusion of phosphorus down linear defect boundaries which are present in EFG silicon or to dislocation pile‐up along these boundaries.

On the deconversion of semiconducting CdF2 crystals due to vacuum heat treatment

Abstract: Crystals of semiconducting CdF2:Mn:Y have been heated under a dynamic vacuum of 1*10-4 Pa at temperatures ranging between 120 degrees C and 700 degrees C for 1-6 h. The results of van der Pauw measurements indicate that the deconversion does not make any difference as far as the initial resistivity of the crystal is concerned if the heating temperature is kept below 250 degrees C. However, above 250 degrees C the resistivity increases in an irreversible manner due to heat treatment, the total rise depending on the duration and temperature of such treatment. Deconversion is favoured by a set of the atomic concentrations of Cd, Mn, and F which have been computed on the basis of microprobe analysis data.